Are Decisive Experiments Possible?

A decisive experiment is a single experiment intended to determine, between two theories, which one is true and which one is false.

According to Kuhn, there is no such thing as a decisive experiment. This is because he thinks of competing theories as being incommensurable.  Incommensurability amounts to the notion that competing theories do not even speak the same language, use none of the same theoretical terms, and so no decisive experiment will be possible.  This is because the meanings of each of the theoretical terms in each of the theories acquires its meaning uniquely from its place or role within its respective theory. A theoretical term, then, is only meaningful in the context of a theory. So any proposition of T1 must be saying something different than any proposition of T2 — they share none of the same concepts, and so there is nothing between the two theories that can be directly compared. And a direct comparison is necessary for a decisive experiment (since it is a single, deciding experiment).

But from a scientific realist perspective, this doesn’t seem quite right. Kuhn’s rejection of a decisive experiment is predicated on the notion that T1 and T2 have nothing in common — they talk about none of the same things (except for, maybe, the direct observable phenomena [sense-data]). But this is a mistaken assumption. T1 and T2 can talk about the same things.  There is no reason to suppose that when T1 makes a claim about electrons and when T2 makes a claim about electrons, that T1 and T2 are not making (different) claims about the very same thing.

This rests on a realist attitude (at least toward theoretical entities). Here’s why I’m a realist about theoretical entities. And given this, I also think that Bohr, Stoney, and Thomson were all talking about the very same natural kind despite their different theories (and theoretical frameworks).  Each of their stereotypes about the electron may have differed (indeed, some of them may have even been incompatible with each other), but this does not entail that the extension of each term was different.  As Putnam argues, meaning just ain’t in the head.  The fact that Bohr, Stoney, and Thomson had different stereotypes associated with the electron does not mean that they were referring to different things — meaning is not determined by one’s mental/psychological state.  Natural kinds, like ‘water’ or ‘electron,’ are (to an extent) indexicals.  That is, they directly refer to their corresponding object without the aid of any definite description.  Here’s how ‘water’ gets its meaning: I point to water and say, ‘Now this is water.’  By using the demonstrative ‘this’ I am directly referring to the thing that I am pointing to — I am not generating any kind of definite description.  Here is how ‘water’ does not get its meaning: ‘I define water to be whatever is that odorless, clear, tasteless fluid of such-and-such density.’  The same is true for the electron.  The electron is whatever we mean to refer to that causes those streaks in the cloud chamber and say, ‘that thing (is an electron).’  We do not have in mind any necessary and sufficient conditions for the use of the term, and do not mean to supply and specify them.

If we accept that Bohr, Stoney, and Thomson were all talking about the very same natural kind, then we might think that decisive experiments are possible (insofar as we can decide, between two competing theories, which one must be false). Suppose T1 makes a claim p about a natural kind, E.  And T2 makes a claim q also about natural kind E.  Further suppose that p and q are incompatible claims. The important thing here is that, whatever the differences between T1 and T2 may be, T1 and T2 are still making claims about the very same, real entities.

We should be able to take E, put it in the appropriate circumstances, and observe whether p or q holds. If neither hold, then neither theory can be true (as per modus tollens). If p holds, but not q, then we reject q as false (and vice versa). If both hold, then there must be some inconsistency in our background theories (to which both T1 and T2 are a part). But suppose that p, in fact, holds and q does not. Because they were both making observable predictions about the very same real, physical thing, the experiment (which must contain the real, physical thing in question) falsifies q and does not falsify p. In this way, we ‘decide’ to accept p over q. But this does not entail that p is true — only that it has not been proven false.

But suppose of you’re of the antirealist, rather than realist, persuasion.  Are decisive experiments still possible?  Generally, with an antirealist view, you really will see two competing theories as genuinely incommensurable, as really speaking two different languages, and all the theoretical entities thereof cannot be identical (for their meaning is derived from their role within the theory).  T1 and T2 cannot assert and q (respectively) about (something like) E.  For the antirealist, there is no E, each T1 and T2 has its own E1 and E2 (respectively) — and E1 and E2 are not identical.  So it follows that there is no common element to link the two for direct comparison.  So, prima facie, it seems like decisive experiments will not be possible.

But I’d like to note that while there may be no such thing as a decisive experiment between T1 and T2, this does not entail that T1 and T2 are incomparable.  There may still be a method for deciding between the two.  If T1 and T2 are both equally empirically adequate, then they adequately predict and organize all the phenomena we have been acquainted with.  Kuhn, if anything, was a keen observer of the history of science.  And one important observation was this.  Within any scientific paradigm, there will eventually (and inevitably) be some phenomena that the concepts, methods, and knowledge of the paradigm cannot account for.  If the paradigm cannot provide an adequate solution, then a revolution or gestalt-switch will occur and a new paradigm, with a new conceptual apparatus, will emerge.  Eventually T1 or T2 (or both) will encounter an anomaly.  If neither can account for their respective anomalies, then T1 and T2 will be abandoned and T3 (or T3 and T4) will emerge.  But suppose T1 can account for its anomaly while T2 cannot (and, moreover, this is an anomaly we really care about).  Then we may well feel just fine about abandoning T2 and pursuing whichever program is suggested by T1.

Crucially, this cannot amount to anything like direct comparison.  And if you think that science progresses toward some kind of truth, then it is possible that we may be led astray.  (Though I do not think we’ll wander too far.1)  But this does seem to be a method for deciding between two equally empirically adequate incommensurable theories, if, albeit, an imperfect one.  There is no one decisive experiment, but a series of experiments within each respectively may eventually lead us to prefer T1 over T2.

  1. Perhaps I will write a post discussing this. 

Confirming the Existence of Theoretical Entities

In the Philosophy of Science, there is some debate over what extent we can ascribe existence to theoretical entities, like electrons (or neutrinos or other particles).  Theoretical entities are ‘unobservable,’ meaning that we can never directly perceive them.  Because we cannot directly perceive them, some philosophers, like Van Fraassen, maintain that theoretical entities are really just useful fictions — they are concepts that are only meaningful in the context of an empirically adequate theory.  (An empirically adequate theory is one that accurately predicts and organizes relations between observable phenomena.)

I’ll argue that we can confirm the existence of theoretical entities. But this does not entail that we can ‘confirm’ the truth of theories themselves. Before exploring the views of any particular philosopher of this course, I’d like to provide a thought-experiment initially put forward by Dretske. The Martians are planning to invade Earth, but need to do recon first, so they decide to send Martian spies. There are two kinds of spies that they can send, (1) the Martian spy has an invisibility cloak and so can walk Earth unseen by humans, (2) the Martian spy disguises himself as a human (with appropriate makeup and costumes). There’s a wrinkle with (1); though the Martian is invisible, the cloak has certain magnetic properties that attract all metal objects (such that spoons, pans, and so on will attract to and stick to the invisible Martian). In light of this, the Martians decide to go with option (2); despite the fact the Martian is not invisible, there is a powerful intuition suggesting that he is, nevertheless, less detectable. Though the Martian is completely visible, he is seen as a human and does not arouse Earth’s suspicion. Had the Martian worn the invisibility cloak, the humans would be able to detect the Martian presence quite easily — they just have to recognize the strange behavior of pots and pans. The disguised Martian is observable, but less likely to be detected. The point of this example is to show that there are situations where ‘unobservables’ are more easily detected (and the presence of the corresponding object more easily confirmed) than ‘observables.’ The disguised Martian is observable, but less likely to be detected. Consequently, we shouldn’t put much stock in any rigid demarcation between observable and unobservable entities.  Rather, it seems like there is no real, useful distinction between observable and unobservable entities.

The cloaked Martian is detectable because of the effect he produces, viz. he attracts magnetic objects. That is, we can infer some causal element that produces the observable effects. If we wish to maintain our notion of cause and effect, then we must accept the confirmation of theoretical entities.  Van Fraassen provides arguments against one realist strategy, viz. the ‘inference to the best explanation.’  But inferring the presence of an electron from the streaks it leaves in a cloud chamber (or inferring the presence of a Martian from the unnatural behavior of spoons, pots, and pans) is not an inference to the best explanation.  Rather, it is an inference to the best cause.  And these two kinds of inferences are importantly different.

Here’s the reason Van Fraassen thinks that inference to the best explanation is illegitimate.  An explanation of a phenomenon is not one of the ingredients of the universe.  It is not as though the Author of Nature had written down that there should be various things like entities, qualities, and, additionally, more importantly, explanations.  Explanations are always relative to human interests, they are not things that are true or false about the world.  Our grounds for believing Einstein’s conclusions regarding his photoelectric effect was not because we thought that there was anything particularly explanatory about the photoelectric effect, but rather we believe in it because of its incredible predictive power.  It consistently and accurately arranges observable phenomena in a rational way, and allows us to make predictions.  It provides no veritable explanation of the phenomena in any way that might be said to be true or false.

But inference to the best cause is not a kind of inference to the best explanation.  The two are quite distinct.  From observing the existence an effect, it is not illegitimate to infer existence of a cause.  If the existence of an effect did not entail the existence of a cause, then we cannot make sense of an ‘effect’ at all.  Intuitively, the existence of an effect implies the existence of a cause, for if the cause did not exist, then what is it that brings about the existence of some effect?  This is different from inferring to an explanation, for nothing about the explanation (in and of itself) implies that it should be true (which is analogous to existing).  I can explain (that is, give an account, tell a story) about how Bob Dylan got to Memphis, if you ask, and it will be perfectly adequate, rational, and sensible.  But you cannot infer the truth of my explanation (except on faith in the authority of my exlanations) from the fact that Bob Dylan is in Memphis and I can tell a good story about it.

So what have we said?  From the existence of an effect we can infer the existence of a cause.  But from the existence of an effect we cannot infer the truth of some empirically adequate explanation or theory.  Fortunately these kinds of inferences are not the same.  We have also shown that there is no real distinction between observables and unobservable.  So observing the existence of an effect does not imply anything about the observability of the cause.  We can infer the presence of the cloaked Martian spies the same way that we, by oberving streaks in a cloud chamber, infer the presence of an electron (or some other particle) which caused those observable streaks.  Martian spies and electrons have observable, causal effects — and from this we must infer their existence.

But the most direct confirmation for the existence of theoretical entities comes from intervention in the physical world — experimentation. We can actually interact with these unobservable entities to produce new effects, new observable phenomena. We can ‘spray’ electrons to change the charge on a certain system of particles. If electrons were merely a convenient fiction, then it would be difficult to account for these results.  If we can manipulate the (unobservable) object to produce real, observable effects, then how could we deny the existence of the object?  Van Fraassen might ask, ‘Well whose electron are you spraying?  Bohr’s?  Stoney’s?  Thomson’s?’  The answer is, of course, none of theirs.  We are simply spraying the electron, the very same electron that Bohr, Stoney, and Thomson all took themselves to be referring to.  The existence of an entity is independent from the truth or validity of the theory of which it is a part.  Suppose that Newton is walking through the British countryside when we stumbles across a strange, alien device, an electron emitter.  (Of course, he will not recognize it as an electron emitter.  He has no conceptual apparatus for handling electrons.)  He takes it back to his estate that has a beautiful orchard.  Newton begins playing with the emitter (as Newton was notoriously fond of such tomfoolery1), points it his favorite apples (which happens to be made of niobium), and squeezes the trigger.  Electrons are emitted from the device, strike the niobium apple, and consequently affect the apple’s charge.  When Newton sees the apple drop, he observes that it drops at a rate slower than the rate at which the infamous apple that bonked him on the head had fallen.  Newton could not have observed the cause, but he can observe the acceleration-change of the apple.  (Of course, Newton will be mystified by this, because he does not know what he has done, nor has any of the relevant concepts like electron or ‘charge.’  It is unlikely that he would actually infer the existence of some electron(s) flowing from the emitter.)  The point here is that the existence of entities does not presuppose any corresponding theory or background assumptions about the world.  Entities and theories are separate.  The electron is just the electron.  Bohr’s electron is just the electron in its proper role/context within Bohr’s theory.

(And to really press the point, if an entity owed its existence to the truth of a corresponding theory, then we could never prove the existence of a theoretical entity in the same way that we can never prove the truth of a theory.  For confirmation of a theory comes from continuous and diverse affirmations of the consequence of that theory.  But the affirmation of the consequent can never entail the truth of the antecedent.  [Consequently, theories are only ever disprovable, never provable.]  If the truth of a theory cannot be proven, and the existence of a theoretical entity depends on the truth of its corresponding theory, then the existence of a theoretical entity can never be proven.)

The idea of experimentation or intervention is the best evidence we have for theoretical entities.  It is the fact that we can manipulate these unobservables to create new, observable phenomena.  We use electrons to manipulate our observable world in a way that we otherwise could not.  The only way to really make sense of this is to suppose that electrons really are part of the world, and not just some useful fiction of our devising.

Here’s another way to think of it. Suppose there’s something like a duck-rabbit, and initially I think that it is a rabbit. Indeed, I say that there are rabbits and that this is a rabbit. But suppose on closer inspection I realize that actually what I thought were ears are clearly a bill (how could I be so blind before?). So I forswear my previous assertions: there are no rabbits, that is no rabbit. Now I know that it is a duck. What changed? Clearly there was a gestalt-switch, I once applied ‘rabbit’ to the duck-rabbit and now I apply ‘duck.’ My interpretation of the thing that I am looking at has changed. But it is not as thought the thing that I am looking at (the penstrokes on the page that constitute the duck-rabbit) has changed at all. The lines are still there, arranged in exactly the same way. Physically, it is the same as it ever was. The point is this: theory has no effect on what natural kinds of things are out there in the world. The things are simply out there, for us to name them, attribute properties to them, and categorize them as we wish. Our namings, attributions, and categorizations do not determine what is so. Electrons are constituents of the world like the inkstrikes that are constituents of the duck-rabbit. We determine the role that electrons play in our theories, but we do not determine the existential status of electrons themselves. (This is like how we determine the role that the arrangement of penstrokes play in our interpretation of the duck-rabbit, but we do not manipulate the strokes themselves.)

  1.  Factually wrong.  Newton hated tomfoolery. 

Quantum Mechanics and Many Minds

In this post I will explain how measurement gives rise to the many minds interpretation (MMI) of quantum mechanics (QM), an interpretation which entails that there are no ‘matters of fact’ about the outcomes of measurements and so no genuine measurement is possible.  Subsequently, I will discuss how this interpretation affects our understanding of QM and the world.

The measurable properties of electrons are called ‘observables.’  When a property of an electron is measured, the observable assumes one of two values.  We will discuss the properties ‘color’ (whose value is either white or black) and ‘hardness’ (whose value is either hard or soft).  We measure an observable by shooting an electron through a property-box which detects and represents the value of the relevant property.  By the uncertainty principle, the properties of color and hardness are incompatible with each other (because they are orthogonal; absolutely no correlation can be made between color and hardness) — the measurement of color disrupts the value of hardness and vice versa.  A way we can put this: an electron that we know is black is in a superposition of being both hard and soft. Superposition requires some explanation.

A superposition is a mode of being or movement for electrons.  A Total of Nothing box (ToN) is a box with two apertures; an electron (E) passes through it with none of its measurable properties changed or affected, and the time it takes for E to clear the box is the same it takes for E to traverse empty space of the same size.  Shoot a white electron through a color-box, and it will exit white.  If we insert a ToN into the middle of the box, the white electron will emerge black instead of white.  But by definition a ToN changes none of the properties of that which passes through, so it follows that the electrons could not have traveled through the ToN and that they could not somehow have circumvented the ToN (for then they still should have exited the box white).  So we say that an electron is in superposition in the sense that it could not have been black and it could not have been white and so it must somehow be in the state of both black and white until it emerges from the box and is determinately either one or the other.

We also need to understand something about the standard view of QM, namely the roles of the dynamical equations of motion (DEM) and the collapse postulate.  DEM is based on the Schrodinger equation, \Psi(t_1) \rightarrow \Psi(t_2), and says that the states of all physical systems invariably evolve in accordance with DEM which are strictly deterministic principles — there is no room for probability (all motions are theoretically calculable).  The collapse postulate, in contrast, is strictly probabilistic.  It says that a system in a superposition (of color, let’s say) collapses to an observable state (to either black or white, with the probability of either outcome being exactly 1/2), when disrupted by some measurement.1 So, prima facie, it seems that physical systems are governed by one set of rules when not being measured (the strictly deterministic ones) and are governed by different set of rules when they are the process of being measured (the strictly probabilistic ones).

But there is something strange about saying that physical systems are governed by two different kinds of rules depending whether or not they are being measured.  That physical systems are probabilistic only when measured (and are otherwise deterministic) seems rather ad hoc, especially in light of the measurement problem.  This is to say that, on this standard view, the probabilistic axiom is postulated solely for the sake of preserving our ability to make accurate predictions.  Moreover, we cannot even determine when the collapse of a physical system occurs — we cannot identify the precise physical interaction which causes the wave function to collapse.2 Suppose we wanted to maintain the (more parsimonious) thesis that all physical systems are governed by the same set of rules at all times.  If this is so, then (we will show) no genuine measurement will be possible.

Let’s make more explicit our assumptions.  Suppose that (1) there is just one world, (2) the world has one true description, (3) QM provides a complete description of any physical system, (4) DEM always makes true predictions, (5) normal people can correctly report whether they have some determinate belief, and (6) the evolution of a person’s mental state during the course of measurement is probabilistic.

(1), (2), (3), and (4) should all strike you as intuitively plausible.  Here’s the idea behind (5).  Though not all of your determinate beliefs (like that there is blog post before you) are immediately present to us in our experience, if we are to reflect on any believable proposition \phi, we would be able to accurately specify or report our (dis)belief in \phi, which has some determinate value.3 We will return to (6).  But notice that all physical systems adhere to DEM; mental states, however, always have a determinate value, so they cannot be governed by DEM and so, by definition, they are not physical systems.4 Let’s see where this takes us.


Sam is about to measure a hard electron E (so E is in (1/\sqrt{2})(|E_b\rangle + |E_w\rangle)).  If both QM and Sam’s ability to measure color are true, then after the measurement the physical state of E and Sam’s brain is (1/\sqrt{2})(|believesE_b\rangle|E_b\rangle + |believesE_b\rangle|E_b\rangle) (by DEM).  But if you ask Sam about the outcome, he would report that he has a definite belief (e.g., Sam reports his state as: |believesE_b\rangle).  So Sam’s brain state cannot have any definite belief about the outcome.  But we can report our mental states (so they must be determinate) (via [5]).  If this is so, then our mental states are not identical to physical states.  We demarcate mental states and brain states by asserting that the evolution of Sam’s mental state is probabilistic.  Sam’s mind (which is not his brain or brain state), begins the measurement with no beliefs about the state of the outcome, and ends up with a definite belief (a mental state), e.g. |believes E_b\rangle.  Sam’s beliefs (mental), are never in superposition.5   The probability of Sam being in a mental state (e.g. |believesE_b\rangle) after measurement is exactly 1/2.  The mind associated with a brain ends up in a mental state (e.g. |believes E_b\rangle) associated  with one of his brain states e.g. the brain state 1/\sqrt{2}(|believes E_b\rangle + |believes E_w\rangle) (that is — the mental state is one of the two terms of the [superpositional] brain state).

But if the mind is associated with just a single brain state in the superposition of brain states, then all but one of the brain states (which we represent: |B\rangle =c_1|\acute{B_1}\rangle +c_2|B_2\rangle +c_3|\acute{B_3}\rangle + ... + c_n|B_n\rangle, where |B\rangle is the overall brain state6) represent mindless hulks in the sense that there is a potential infinity of brain states with no corresponding mental state.7 We correct this by supposing that every sentient physical system is associated with a continuous infinity of minds8 as opposed to a single mind and that probability of some infinite subset of those minds in a particular time, is given by |\langle b_i | \Psi \rangle|^2, meaning when the outcome of Sam’s measurement is a superposition, 1/2 Sam’s continuous infinity of minds will be |believesE_b\rangle, and remainder is |believesE_w\rangle.  The reason for supposing an infinite collection of minds is so that each mind will end up associated with some element of the brain state in the superposition resulting from measurement; a measurement or a sequence of measurements may have an infinite number of outcomes, so an infinite number of minds is required (to guarantee that every brain state will have a corresponding mental state).  When Sam’s brain is c_k|B_k\rangle, his mind is in a determinate mental state |M_k\rangle.  Each individual mind in the continuum still evolves probabilistically and will never be in superposition (in the same manner as previously discussed).  But the totality of the infinite set of minds (thglobal’ mental state) associated with some c_k|B_k\rangle evolves deterministically since the evolution of the measurement process is deterministic.9 The evolution of the global mental states will be determined, but the course of each individual mind will be subject to QM probabilities.  DEM determines the evolution all physical systems, including brain states, and the varieties of brain states determine the possible mental states (what beliefs Sam can collapse to and so have), so mental states will depend on what brain states are present and thus the determined physical state of the world.


Let’s revisit Sam’s measurement of E.  He is |B\rangle and no mind has |color beliefE\rangle.  After the measurement, Sam’s brain state will be (1/\sqrt{2})(|believes E_b\rangle + |believes E_w\rangle), by DEM. 1/2 Sam’s minds will be |believes E_b\rangle and the other 1/2, |believes E_w\rangle.  Each mind can be thought of as a unique ‘POV,’ representing some state of affairs, and each mind will have a seemingly continuous experience.10 So the 1/2 minds associated with |believes E_b\rangle are in a different ‘mental world,’ so to speak, than the other 1/2.

This has a curious consequence: our beliefs about physical reality will turn out to be false.  This would be problematic, except for that the future evolution of Sam’s mental states will proceed exactly as if his beliefs were true.  Prima facie, this seems like a bitter pill to swallow.11 But it needn’t be too bitter, for our beliefs have effective validity — they will always evolve as though they were true.  Suppose that after Sam’s measurement (which happened at t), Sam_1 is associated with |believes E_b\rangle.  Sam_1 repeats the measurement with same E and the physical outcome is12 1/\sqrt{2}(|believes E_b\rangle|D_b\rangle|E_b\rangle + |believes E_w\rangle|D_w\rangle|E_w\rangle.  Sam’s mental state must be |believes E_{b_1}\rangle|believes D_{b_1}\rangle + |believes E_{b_2}\rangle|believes D_{b_2}\rangle, because all his minds_1 after t know that the value of measurement_2 must be |E_b\rangle, for empirically the outcome of E_b going through a color box (without any other tampering) must be E_b.  But this is the same mental state that Sam would have ended up in had in the event that his belief about the first measurement (at t, which was false) were true, for suppose measurement_1 resulted in |D_b\rangle|E_b\rangle (corresponding to his belief) instead of the superposition — then measurement_2 must result in |believesE_b\rangle|E_b\rangle for the minds know that if E_b goes through a color box the outcome is E_b and this is entailed by DEM.  The fact that our beliefs about reality are false has no effect on our lives or what we take to be our experience of the world.  We shouldn’t be too resistant to accepting that most of our beliefs our false, because if it happened to be the case that our beliefs were true, there would still be no detectable difference in our perceptual experience.  We won’t end up questioning our beliefs, even if we know them to be false about veridical reality, because we will still believe that the fire we (falsely) believe to be before us is hot — for if we do not, then we will likely get burned; so our beliefs must be valid even if false.


An important consequence of this view is that it preserves locality.  On the many minds picture, it is an illusion that measurements have outcomes (for measurements like Sam’s will result in a superposition), while the underlying assumption of nonlocality is that measurements do have outcomes.  At the conclusion of Sam’s measurement, the physical state of E is just 1/\sqrt{2}(|E_b\rangle + |E_w\rangle), and so there is no determinate outcome.  No matter what outcome is measured by whatever half of Sam’s continuous infinity of minds, one half of the minds will be |believes E_{b_1}\rangle and the other half, |believes E_{w_1}\rangle.  This is not, however, a local realist theory.  Our beliefs will always be determinate and so we will always be in a belief state representing locality, but the actual state of the physical world is in superposition so veridical locality can never in fact be established (again because measurements do not have outcomes).

While it may seem problematic that mental states (and their probabilities) are inserted into this view by fiat, it is not necessarily so.  For the physicalist, the aforementioned seems ad hoc, inserted for the sole purpose of accounting for QM probability distributions.  This inevitably weakens the theory (as argued by Hempel).  This worry gets traction from its physicalist assumptions.  But prima facie, we are not compelled to physicalists over dualists; our inclination toward one over the other is contingent upon whatever background hypotheses we entertain and which concepts we choose to take as primitive (as argued by Lakatos).  If we take perceptual experience to be primitive in the same sense as matter or energy,13 then physicalism does not have any prima facie advantage over dualism.  And so, if we start with these equally plausible dualist intuitions, then MMV actually accounts for why our perceptual experience is such as it is, in a way that is both parsimonious and not-ad hoc.14  But moreover, because on MMV mental states still depend on brain states, we can preserve our intuitions about the brain somehow determining the state of our minds — and so stay consistent with contemporary psychology and neuroscience.


We’ll conclude by summarizing what we have shown MMV means for QM and the world.  All physical systems turn out to be governed by DEM, so there is no need to square DEM with the collapse postulate.  This also entails realism, that there is some one correct physical description of the world at any $t$, and that description will not be changed or altered by consciousness or other non-physical phenomena.  Because the evolution of the physical world is determined by DEM and is quantum mechanical, the ‘global’ mental state of Sam is fixed by his physical brain state — that is, mental states importantly depend on physical brain states.  Locality is preserved.  Probabilities (which is where the collapse postulate came in) turn out to be objective but can only refer to sequences of mental events in individual minds.  And measurement will not be possible because there is simply no matter of fact about the outcome of the measurement (because the measurement will result in superposition).

  1. That is, the states of systems undergoing measurement evolve in accordance with the collapse postulate, not DEM. 
  2. Does it collapse when the microscopic particle interacts with the macroscopic measuring device?  Or does it collapse when the information from the position of a measuring dial passes through our retina into our visual cortex?  There is no good means of determining this.  A theory invoking collapse ought to what, where, when, and why the collapse occurs. 
  3. It does not matter if there are degrees of belief, for even if there were, we should be able to assess the exact degree of our belief in \phi
  4. Here’s the main thrust: if an observer can measure some property of an electron and can correctly report his mental states, then it cannot be the case that his brain state is identical to his mental state, for brain states are physical systems conforming to DEM (and so will be superpositional) while mental states are never in superposition and so will be better described by the probabilities of the collapse postulate. 
  5. This explains why we never see a superposition.  Your perceptual experience, like your seeing a tree, amounts to a representational belief state. Because this is a mental state, there is no experience of superposition, and all beliefs are definite and of definite things. 
  6. I.e. the totality of all occurrent brain states.  Note: each |\acute{B}\rangle term is associated with an infinite set of minds in the corresponding mental state |M_k\rangle.) 
  7. As thus far we have made it sound like there is some one mind corresponding to the mental state associated with a some, one, brain state.  Consequently, the remaining brain states have no associated mind. 
  8. A continuous infinity of minds can be thought of as the mental (or dualist) analogue of Everett’s continuous infinity of worlds. 
  9. This will become clear in the next example, but the idea is that the physical superpositions are determined, and each mind collapses to a mental state associated with one term of the superposition, so the totality of the evolution of the mental states will be determines, but the course of each individual mind will be subject to QM probabilities. 
  10. Similar to how, on the many-worlds view, each world represents some outcome of physical affairs/measurement, and no person notices their continuous instantiation of possible worlds — they will have a continuous experience. 
  11. For, on reflection, it seems as though our beliefs turn out to be true, and that we organize our lives around these beliefs that do correspond to reality in some determinate way. 
  12. The term ‘D‘ represents the measuring device. 
  13. As has been done here: ‘Facing Up to the Hard Problem of Consciousness,’ David Chalmers. 
  14. It is parsimonious because it simply explains the evolution of both physical systems and mental systems; it is not ad hoc because there is no reason to think that ontologically distinct systems should be governed by the same set of rules. 

On Scientific Observation

Consider the following two statements describing the nature of scientific observation. (A) All observation is theory-laden.  And (B) all observation starts with raw-sense data.  I suspect that (A) describes that nature of scientific observation much better than (B), and will endeavor to briefly sketch out why.

In making any observation, we must make use of certain concepts that affect the way in which we see such-and-such.  For instance, if you draw someone a duck-rabbit and ask, ‘what do you see?’ they will either (1) see nothing (that is, apply no concept), (2) see a duck, or (3) see a rabbit.  But they cannot simultaneously see some combination of (1), (2), or (3).  So what you see is contingent upon what concept you choose to apply.  Here’s a more historical example. Aristotle saw a pendulum as a natural object that is ‘seeking’ to come to the natural state of rest.  He swung the pendulum, and gradually its period approached zero.  This confirms the theory that objects seek a natural state of rest.  Galileo, on the other hand, saw the pendulum as a natural object that was almost maintaining its inertia.  And the fact that a pendulum oscillates confirms that objects in motion actually ‘seek’ to stay in motion.  Galileo and Aristotle confirmed each of their contrary theories with the same exact data and observations because of the differences in their background knowledge and conceptual resources.

If observation got off the ground with sense-data then it is difficult to see how we could come to even see a duck or a rabbit in the duck-rabbit.  If we have no background theory, then it seems that we do not even have the resources to apply a concept to the image.  Without some concepts or assumptions about either ducks or rabbits, we can only ever see the duck-rabbit as pen-strokes on a page.  Ideas of induction and causation are not present in raw sense-data either.  But it seems that causation and induction are required in order to form a hypothesis like, ‘rocks fall when dropped.’  No finite number of observations in sense-data could justify this claim without presupposing a causal connection or the legitimacy of inductive inference.  It requires the assumption that something about rocks makes it such they they fall if unsupported.  These kinds of ideas must be part of the background when making some hypothesis — when articulating what it is that you are seeing.

There is an interpretive step between sense-data and any proposition you may use to characterize it.  Lakatos point out that propositions can be derived only from other propositions and cannot be derived from an empirical fact observed in sense-data.  There is a fundamental distinction between the data we strictly observe and the language that we use to articulate that observation.  Language immediately straightjackets our observations in the conceptual framework of thought or language — all empirical propositions are the recipients of some kind of interpretation (which will come from some kind of [primitive or not] background theory).  Consequently, any thinker or language user must see things in some interpreted way — for the language user, there is no uncorrupted sense-data, it is all theory-laden.

Moreover, if we hope to form any scientific hypotheses at all, then we cannot begin with raw observation, for we will have no way of selecting which observations to treat as relevant.  We must approach observation with some kind of expectation or background theory in mind in order to know what to look for, to know what kind of data we are interested in collecting.  This is a pragmatic point — we simply cannot note and observe a possibly infinite set of sense-data and then try to find regularities within that.  And even if we did, what sort of regularities we find depends on what sort of patterns we are looking for.  We must interpret data through some theory or other to even recognize which patterns in the data are regularities and which are just happenstance or coincidence.

Furthermore, science just isn’t about the raw sense-data.  As Schlick points out, science is about the discovery of laws and relations that exist between features of the given — it is not about the particular atomic features of the given itself.  Consequently, observation cannot start with raw sense-data, for we must actively impose laws and regularities of our own devising onto the atomic features or sense-data and observe what holds (as pointed out by Popper — we form a hypothesis and then seek to falsify it).  We are looking to observe what regularities hold in our experience/sense-data, we are not looking to observe a particular atomic feature of sense-data.  These regularities must be imposed by conjectures — and these conjectures provide the background theory that color our observation or commits it to certain concepts couched in our language (for all conjectures must be expressed linguistically).

So (A) is better.


Scientific Progress

Let’s take ‘scientific progress’ to mean something like ‘moving closer toward a ”correct” conception of reality.’  If this is so, we might ask whether progress is better achieved through methods of falsification or through Kuhnian-style revolution.  I suspect the former, and will briefly explain some of my thoughts.

Popper claims that the goal of science is to move to some sort of objective truth.  This seems right.  Intuitively, there is some one way that things are, that we might better describe or represent as we move  from some scientific model M to a better scientific model N.  Revolutions, on the other hand, are predicated on some sort of ‘gestalt-switch.’ A revolution isn’t just the emergence of a better fitting theory, it is a complete replacement of the particular scientific enterprise’s conceptual apparatus and framework, incompatible and incommensurable with the theories that came before.  A reconception does not entail an advance. 1

If we think that there is some true, or ‘correct,’ conception of physical reality, then falsificationism will reliably lead us toward some correct picture.  The feature that gives falsificationism its tight relationship to reality is its reliance on a sort of infallible, deductive method, modus tollens. 2  The affirmation of the consequent of a hypothesis does not entail the truth of that hypothesis, but the negation of the consequent of the hypothesis does entail the falsity of the hypothesis.  We cannot definitively ascertain the truth of any hypothesis (for confirming the implication of a hypothesis does not entail the truth of hypothesis — perhaps there are other ways that the test implication could have turned out true), but we can definitively know its falsity.  We move toward a more correct conception of reality by deducing ways that the world could not be — eliminating false hypotheses — in order to narrow down the scope of possibly true hypotheses or ways that the world could be.  Narrowing the range of possible truth marks an advance toward a correct conception of reality.

It is important to observe that we only consider salient or otherwise relevant hypotheses.  Or else you might suppose that there are an infinite number of ways that the world could be, and the elimination of any number of hypotheses doesn’t narrow down the field (for \infty - n is just \infty).

Simply falsifying theories is not enough, however.  For some falsifying results are due to instrumental error (for instance, when it was ‘discovered’ that neutrinos could travel faster than the speed of light), or perhaps the falsity of some background hypothesis.  In the spirit of Lakatos, we should not throw out a theory until we have a better one to replace it (one with more explanatory power, or is consistent), which has excess content over the unrefuted content of its predecessor. 3  This acknowledges the history of scientific progress — it is not necessary that we have falsified the hypothesis under question, for we may have falsified a background assumption instead.  Consequently, our tests don’t tell us that our hypotheses are false, but merely inconsistent.  (That is, we have a set of hypotheses we take to be true.  In testing a hypothesis, its falsification only tells us that the hypothesis does not fit with how we take the world to be [and how we take the world to be is inevitably steeped in other theories.)  The correct conception of reality is going to be one that maximizes explanatory power and consistency, (and arguably simplicity), for there are myriad ways to describe laws and relations in the natural world and intuitively there seems no reason to suppose that, if two theories have equal explanatory power, consistency, and simplicity, then one of them must be false.  Rather, it seems like the same story is being told in two different languages.  Both are correct conceptions.  But we are spurred toward closer representation of reality by advancing through more and more complicated scientific models as we develop a consistent set of theories with explanatory power.  This is a move toward best-representation, if you will.

Because revolutions are more gestalt-switch 4 than they are progress re vera, they don’t move toward a correct conception of reality.  Indeed, Kuhn argues that no paradigm is closer to ‘the ideal,’ but are rather selected for their ‘puzzle-solving’ capabilities.  This sort of thing should not move toward a closer conception of reality.  Puzzle-solving is something arbitrary.  What is or is not considered a puzzle is contingent upon the current paradigm. 5  Instrumental applicability in a domain relativizes the scientific enterprise to a specific, arbitrary set of problems.  A revolution is not required to respect the puzzles of the paradigm it is revolting from — the reconception reconceives the problems of science.  So we only ever explore some new way of conceiving of reality rather than progress toward some better model, picture, or representation of it.

A revolution provides a new paradigm, a new way of observing and analyzing, but progress must still be made through falsification.  It is by observing effects that were not predicted by our theories (a sort of falsification) that forces us to come up with some better explanation — an explanation which may or may not already be given by the model/framework we are in.  Revolution is not necessitated — the falsification provides all the impetus we need.

Consider the noble duck-rabbit (a visual gestalt).


Seeing the duck-rabbit as a duck and then afterward as a rabbit does not bring you any closer to a correct conception of the duck-rabbit, just a different one.  But by discovering what won’t do as an explanation forces you to work toward some solution that is not subject to the same counterevidence, and so the model continually becomes a better fit or picture of reality.

The result of a revolution is that we see the data with a different conceptual framework.  But the result of (Lakatos’s) falsificationism is that we develop a model that more accurately represents the data.  The latter brings you closer to some goal.  The former does not.


  1. An example of a revolution would be our replacement of the Newtonian mechanics paradigm with relativity or QM.  A complete evolution of our scientific, conceptual apparatus. 
  2. Modus tollens is the following.  P \rightarrow Q. | \neg Q. | \therefore \neg P.  Contrast with modus ponens: P \rightarrow Q. | P. | \therefore Q.  What is not a logical rule of inference is: P \rightarrow Q. | Q.  | \therefore P
  3. Theories build on each other.  That a theory is falsified does not mean that all the content of that theory is false. 
  4. A gestalt is when only one theory or another can be applied toward a set of data at a particular time.  The switch is when you move from applying one concept and instead apply another. 
  5. The conceptual framework of a scientific enterprise determines the nature and direction of the work — that is, what puzzles are important to solve.  ‘Normal science’ consists in the application of the paradigm to more practical scientific problems and questions.  When a puzzle is encountered that the paradigm cannot possibly answer, then a crisis ensues, followed by some kind of revolution. 

Burns on Trump: 2016 Stanford Commencement (Excerpt)

Ken Burns excerpt:

For 216 years, our elections, though bitterly contested, have featured the philosophies and character of candidates who were clearly qualified. That is not the case this year. One is glaringly not qualified. So before you do anything with your well-earned degree, you must do everything you can to defeat the retrograde forces that have invaded our democratic process, divided our house, to fight against, no matter your political persuasion, the dictatorial tendencies of the candidate with zero experience in the much maligned but subtle art of governance; who is against lots of things, but doesn’t seem to be for anything, offering only bombastic and contradictory promises, and terrifying Orwellian statements; a person who easily lies, creating an environment where the truth doesn’t seem to matter; who has never demonstrated any interest in anyone or anything but himself and his own enrichment; who insults veterans, threatens a free press, mocks the handicapped, denigrates women, immigrants and all Muslims; a man who took more than a day to remember to disavow a supporter who advocates white supremacy and the Ku Klux Klan; an infantile, bullying man who, depending on his mood, is willing to discard old and established alliances, treaties and long-standing relationships. I feel genuine sorrow for the understandably scared and—they feel—powerless people who have flocked to his campaign in the mistaken belief that—as often happens on TV—a wand can be waved and every complicated problem can be solved with the simplest of solutions. They can’t. It is a political Ponzi scheme. And asking this man to assume the highest office in the land would be like asking a newly minted car driver to fly a 747.

As a student of history, I recognize this type. He emerges everywhere and in all eras. We see nurtured in his campaign an incipient Proto-fascism, a nativist anti-immigrant Know Nothing-ism, a disrespect for the judiciary, the prospect of women losing authority over their own bodies, African Americans again asked to go to the back of the line, voter suppression gleefully promoted, jingoistic saber rattling, a total lack of historical awareness, a political paranoia that, predictably, points fingers, always making the other wrong. These are all virulent strains that have at times infected us in the past. But they now loom in front of us again—all happening at once. We know from our history books that these are the diseases of ancient and now fallen empires. The sense of commonwealth, of shared sacrifice, of trust, so much a part of American life, is eroding fast, spurred along and amplified by an amoral Internet that permits a lie to circle the globe three times before the truth can get started.

We no longer have the luxury of neutrality or “balance,” or even of bemused disdain. Many of our media institutions have largely failed to expose this charlatan, torn between a nagging responsibility to good journalism and the big ratings a media circus always delivers. In fact, they have given him the abundant airtime he so desperately craves, so much so that it has actually worn down our natural human revulsion to this kind of behavior. Hey, he’s rich; he must be doing something right. He is not. Edward R. Murrow would have exposed this naked emperor months ago. He is an insult to our history. Do not be deceived by his momentary “good behavior.” It is only a spoiled, misbehaving child hoping somehow to still have dessert.

And do not think that the tragedy in Orlando underscores his points. It does not. We must “disenthrall ourselves,” as Abraham Lincoln said, from the culture of violence and guns. And then “we shall save our country.

This is not a liberal or conservative issue, a red state, blue state divide. This is an American issue. Many honorable people, including the last two Republican presidents, members of the party of Abraham Lincoln, have declined to support him. And I implore those “Vichy Republicans” who have endorsed him to please, please reconsider. We must remain committed to the kindness and community that are the hallmarks of civilization and reject the troubling, unfiltered Tourettes of his tribalism.

The next few months of your “commencement,” that is to say, your future, will be critical to the survival of our Republic. “The occasion is piled high with difficulty.” Let us pledge here today that we will not let this happen to the exquisite, yet deeply flawed, land we all love and cherish—and hope to leave intact to our posterity. Let us “nobly save,” not “meanly lose, the last best hope of earth.”

Burns is on point.  There was a time when we expected more from our politicians and representatives, and especially from any candidate for president.  There was a time when we were better men.  Now we are so desperate for an icon that we buy into the cheap tricks of a confident charlatan, muttering the somber refrain, “so it goes.”

It is not my intention to turn this into a political blog.  Considering the danger that Trump poses to the country, however, I would be remiss if I did not express (at least some) of my thoughts.  Consequently, I suspect there may be some more Trump-posts before November.

Solipsism, Logical Positivism, and Verificationism

In this paper I will reconstruct and explain verificationism. Subsequently, I will show how the acceptance of verificationism leads to solipsism, the view that one can have knowledge only of their own mental life, by pointing to a necessary difference in meaning between first-person and third-person mental predicates.

The main thrust of verificationism is this. A statement is meaningful only if it is logically verifiable. The only statements that are logically verifiable or knowable are those which reduce to some description of the given. The given is the domain of all that is knowable; it is roughly your perceptual experience at some particular point in time. The given should not be confused with the terms ‘the internal world’ and ‘the external world,’ both of which are meaningless for the verificationist. This is because propositions like ‘there is an external world,’ will turn out to be not logically verifiable (for the truth or falsity of the fact makes absolutely no change in our perceptual experience). All difference in the given is detectable. Because the given is what is presented to you in perceptual experience, there can be nothing in the domain of the given that is undetectable.

Features in the given are describable with atomic words or atomic sentences. Atomic words, like green, pain,1 and so on, can only be known by ‘pointing’ to some feature of our perceptual experience. They cannot be understood in terms of other words. The word’s meaning is established by the agreement of the reactions of others. That is, the use of the word occupies the same relational-role in the given as it is experienced by each of us. For the verificationist, the question of whether the phenomenal quality of his green-experience is identical to the phenomenal quality of my experience, is meaningless. This is because fact is not logically verifiable.

All propositions ultimately reduce to some sequence of atomic words, whose meaning directly describes the given. ‘There is a deer by the bush,’ reduces to ‘there is a brown spot with such-and-such features by that green spot arranged in so-and-so way.’ To see this, suppose that a proposition’s meaning is something over and above its determining some state of affairs in our perceptual experience. If this additional meaning is expressible, then it would be a (complex) proposition (and so nothing over and above an atomic description of some feature of our perceptual experience). But if the meaning is not expressible, then it cannot mean anything, for that which expresses nothing means nothing. So the truth or falsity of a proposition must correspond to a difference in the given in order to be meaningful.

It follows from this that the meaning of a proposition is identical with its verification in the given, for we verify ‘there is a deer by the bush,’ by observing a familiar arrangement of brown situated by another familiar arrangement of green, and perhaps some audible rustle — for this is what is present in the given. So if we cannot conceive of some verification in the given of the fact, then the fact means nothing. So, a proposition is meaningful only insofar as it is logically verifiable. A meaningful statement says that under certain conditions, certain data appear. (For such a statement to be verified re vera, is for there to be consistent agreement in the reactions of a sufficient number of persons to a given stimulus — an agreement that under certain conditions, certain data appear. In this way, hallucinations and illusions will not be verifiable. For example, the meaning of ‘pain’ is grounded in the fact that many people react the same way to a painful stimulus and would describe or talk about the experience using the same or similar words.)

But we should be reluctant to accept verificationism. For if we do, then we fall into solipsism — I can never know that you have a mental life like mine, that the given confronts you as it does me. Here’s how.

To know when to ascribe mental predicates like, ‘is in pain,’ to others, I must know what it means to be in pain. (For if I do not know what pain means, then I could not even have any thoughts about pain.) On verificationism, the meaning of ‘is in pain’ is identical to its method of verification in the given — I see her wince, say ‘ouch,’ or recoil in such-and-such a fashion, for these are the data in the given associated with the fact.2

But how do I know to ascribe ‘is in pain’ to myself — what is the method of verification in first-person ascription? Schlick argues that mental propositions like, ‘I am in pain,’ are verified in just the same way as propositions like, ‘that Sirius has a satellite.’ (99) That I was in pain yesterday can be verified by examining others’ statements about my behavior yesterday, or happening upon a note that I had written reporting my pain.

But this cannot be my method of verification for asserting (in the first-person), ‘I am in pain.’ For I know that I am in pain only when I experience the sensation of pain. If I am not experiencing the sensation of pain, then I cannot know that I am in pain (and so will not ascribe ‘is in pain’ to myself). For suppose I observe my limbs flailing in the pain-characteristic way, but am experiencing no sensation of pain. I would not come to ascribe ‘is in pain’ to myself; more likely, I would just puzzle over why my limbs were moving such a way. Someone else may ascribe ‘is in pain,’ to me on the basis of my behavior — and while such an ascription seems reasonable, I know that it is not true.  I may even correct them, saying ‘I am not in pain,’ and, if they take my word, that should count as verification for them of the fact I am not in pain.3

Or, I may suppress all my pain behaviors, this does not entail that I do not experience the sensation of pain and so know that I am in pain. Nor is it after I wince that I know my stomach is in pain, rather the wince is must be a reaction to the sensation. I do not verify that I am in pain by observing my behavior or pain report, rather I verify it by ‘looking inward’ as it were, and finding no sensation of pain. The takeaway is that the methods of verification for ‘X is in pain,’ are necessarily distinct between the first and third-person ascriptions. Self-ascription is on the basis of private sensation; other-ascription is on the basis of the others’ observable behavior or report.

Recall that on verificationism the meaning of a statement says that under certain conditions, certain data appear. So perhaps Schlick would say that the first-person meaning of pain is that, under such-and-such conditions, I met with certain data, viz. pain sensations. And while this is reasonable, it is not the sort of thing that can be verified by anyone else. For it is logically impossible that I can have access to another person’s experience (for my experience is necessarily mine), and by the same token, it is logically impossible that another person can verify that I am in pain via accessing my sensation of pain in my perceptual experience.

Suppose I wish to have been Archimedes, running naked down the streets of Syracuse, crying ‘Eureka!’ I enter an ‘experience-machine,’ and have the experience of running through Syracuse. But this is my experience, not Archimedes’; the referent of my ‘I’ thoughts is me, not Archimedes. For if the referent of ‘I’ were Archimedes, then I would simply be Archimedes and could have no thoughts of my non-Archimedean self to which I could associate my experience-machine experiences. The takeaway is this. If you can genuinely access another person’s experience, then you are simply that person, and if you were to ‘have the experiences of another person’ then that is your experience of what-it-is-like to be someone else and you have not genuinely accessed their experience. Whence the logical impossibility. So I can only verify that ‘I am in pain’ through my experience or sensation of pain (which we have shown is necessarily private), and I can verify that ‘she is in pain’ only through observing characteristic behaviors in my perceptual experience (for if she has any sensations like mine, they must be private to her).

Because the meaning of a proposition is identical with its verification in the given, it cannot be the case that ‘I am in pain’ means the same thing as ‘she is in pain.’ To say ‘she is in pain’ is to say that ‘she is moving her limbs in such-and-such a way’ or ‘if we scanned her brain, we would observe the firing of c-fibers.’ Whereas ‘I am in pain’ is to say that ‘I have a sensation of pain.’ From this it follows that I can never say, ‘she is in pain,’ and mean something like, ‘she is experiencing a sensation of pain,’ for this would not be logically verifiable (from my perspective). When Suzie says, ‘I am in pain,’ what she means is something different from what I mean when I agree, ‘Suzie is in pain.’ When she uses the first-person, she is referring to her sensation, but when I use the third-person, I can only refer to her behavior or report. But if she were mute and suppressing her behavior, she is either experiencing the sensation of pain or not, and while Suzie can verify it for herself, it is impossible that I could ever verify it. Let’s say I take ‘is in pain’ to mean only the third-person sense and take ‘S’ to refer to what I know to be my perceptual experience of the sensation of pain, then I can never know if any other person experiences (some degree of) S when I ascribe ‘is in pain’ to them.

I cannot verify that another person has a sensation of pain in the way that I do. This means that I cannot verify that mental predicates, like ‘is in pain,’ apply to others as I must apply them to myself. But if this is so, then I cannot know whether or not someone is experiencing some private mental sensation (e.g. of pain) as I do. So all I can know is my own perceptual experience and mental states. And this matches the characterization of solipsism that we have provided.

The verificationist may reply the following way. Because our question regarding the ascription of ‘S’ to others is not logically verifiable, it has no meaning. It isn’t false that others have mental lives, nor is it true — we simply do not know what it would mean. All it means to have a mental life is to have a certain neurophysiological structure and behave in a certain way.

This reply, however, is ineffective. If I know my S, then I know that there is a unique kind of mental experience ascribable to me. But if the question of other persons’ mental life is meaningless, then my own mental life is incommunicable, for when I tell someone ‘I am in pain,’ I will mean one thing but be saying another.4  Anything else that I might ascribe a mental life to must mean something other than how I mean it when I ascribe it myself, for the question of others’ having perceptual experiences and sensations is meaningless.

Anything else that I might ascribe a mental life to must mean something other than how I mean it when I ascribe it myself. On the verificationist view, mental life just means some kind of behavior pattern. But when we ask the solipsistic question, we do not mean to ask about behaviors, we mean to ask whether other people have mental lives in the sense that I do, whether pain hurts for them as it does for me. This is outside the given, and unknowable.  And this certainly is solipsism.

  1. For such a description of pain can only amount to something like, ‘pain hurts,’ ‘pain is the opposite of pleasure,’ or ‘pain is what makes you recoil.’  The first is a tautology, the second is almost as trivial, the third overbroad and not necessary, and none of them convey any nontrivial knowledge about what pain actually is to the person who has never experienced it. 
  2. Keep in mind. Schlick maintains that the meaning of a proposition is communicated only if it is verifiable. 
  3. Even so, for them to verify that I am not in pain required a characteristic behavior/report from me, whereas my knowledge came from my sensation. 
  4. Ironically, this creates a situation where, far from worrying about the reality of the mental lives of others, we end up worrying how we could ever communicate to others that we have a mental life.