Legitimate Conclusions of Wigner’s Friend Paradox

Seyyed Bahram Borgheai

Abstract

Wigner’s Friend paradox is an argument which Wigner has used to illustrate thecausal role of consciousness in the measurement problem. In this paper, we first look indepth in his stated pre-suppositions and will introduce some more implicit ones which arenot mentioned explicitly by Wigner. In the analysis of the argument, it will be illustratedthat Wigner is not successful in reaching his goal and therefore the causal role ofconsciousness cannot be legitimately entailed from the paradox. Rather, one of the mostimportant conclusions of the paradox is the communicability of conscious observationknowledge for others (conscious observers) for which one of the pre-suppositions shouldbe eliminated. This may result in inter-subjectivity which can be a host of futureinvestigation. Moreover, another legitimate way of resolving the paradox is to reject oneof implicit pre-supposition which is the completeness of standard quantum mechanicsabout some aspects of conscious related events. This is the main conclusion of the paradoxwhich can be rehearsed from different aspects. Finally, after reviewing some objections tothe paradox and also some other solutions to it, a new formulation of the paradox will bepresented with some modifications over the presuppositions.

Introduction

The measurement problem is one of the most controversial concerns in philosophy of

physics. . On one hand we have linear equation predicting the evolving states of physical

system resulting in superposition states 1 . On the other hand, when we make the

measurement the state of a system nonlinearly goes to one definite state. Therefore what

we have according to the equations of QM is not sufficient to explain this reduction of

states. There are different proposed solutions to this problem. Some are known as no-

collapse theories as many-worlds interpretations and its extensions which are multi-

minded and also single-minded theory. Moreover we have creation at observation claim,

1 When the state of the system is not one of the eigenstates of the system.

ans also GRW, Decoherence and the causal Bohmian QM. Since they are all empirically

equivalent2, scientifically, no one can gain superiority over others.

One of the solutions to this problem is proposed by Wigner (1967) who claims that it

is consciousness which is responsible for the collapse. This claim has been proposed first

in the paper “remarks on the mind-body question” in the form of a paradox known as

“Wigner’s Friend”.

In this paper, first we restate the Wigner’s pre-suppositions in the way he has himself

stated and after presenting the argument, we will deliberately analyze them.

Wigner’s goal of the argument

To clarify the goal of Wigner, it is worth noting that he concedes two promises about

consciousness:

1. Consciousness is irrefutable.

“…it was not possible to formulate the laws of quantum mechanics in a fully consistentway without reference to the consciousness. All that quantum mechanics purports to provideare probability connectionsbetween subsequent impressions of the consciousness, and…. itcannot be eliminated” (Wigner, 1967,173).

Therefore he believes that consciousness cannot be rejected and Moreover, it is

necessary for explanation of QM.

2. Consciousness has a causal effect on body.

This last premise is what Wigner has proposed his argument (the paradox) for. He

intends to show the active role (responsible or causal role) of consciousness in reduction

of a superposition state to a determined state in measurement problem as an example of

this causal effect of mind over body. In this paper we are investigating whether the

paradox is well designed to reach this goal. But before stating his paradox let’s analyze his

pre-suppositions.

2 Practically of course, since there may be some thought experiments which results differently due todifferent interpretations, such as one that is mentioned by Albert and Putnam which behaves differently inBohmian and Single-minded theories.

Pre- Suppositions

PS1.Definition of existence:“The statement that it "exists" means only that: (a) it can be measured, hence uniquely

defined, and (b) that its knowledge is useful for understanding past phenomena.” (Wigner, 1967, p174)

PS2. For each entity, all the related knowledge can be given by its wave-function.

The important point here is that Wigner assigns the wave-function toknowledge rather than ontologically to an objective entity.

“In fact, the wave function is only a suitable language for describing the body ofknowledge-gained by observations-which is relevant for predicting the future behaviorof the system. “ (Wigner, 1967, p 175)

PS3.The information which the wave function gives us is communicablewith (or

transferrable to) others.

“ The communicability of the information means, in the present example, that ifsomeone else looks at time t, and tells us whether he saw a flash, we can look at time t +1 and observe a flash with the same probabilities. “ (Wigner, 1967, p176)

It means that it does not depend on who the observer is and moreover, the probability

is similarly observer independent, i.e.objective. In this way, together with the previous

assumptions, Wigner claims that the wave functions ‘exist’.

PS4.The consequence of our observation, or in Wigner’s literature, the impression

gained by interaction with a system, changes the wave function. The reason, in his view, is

the entrance of data (or information) into one’s (observer’s) consciousness and changing

of his expectation.

“… it is the entering of an impression into our consciousness which alters the wave

function because it modifies our appraisal of the probabilities for different impressions

which we expect to receive in the future. “ (Wigner, 1967, p177)

In other words, reception of an impression affects our expectation (or probability) of

reception of another impression and therefore changes the probability and also the wave

function.

These are pre-suppositions which Wigner himself explicitly has stated but there are

some other implicit pre-suppositions which will be enumerated later.

Critical evaluation of Pre-suppositions

PS1:

Wigner reduces, in most positivistic way, the existence to ‘be measurable’ and ‘being

useful’ for scientific explanation. By and large, with this positivistic definition of

existence remaining metaphysically realist is not possible. By the way, when he intends to

give a causal role to consciousness by his argument, its measurability is under question.

Thus he needs to redefine (or extend the domain of his definition of) the existence.

Therefore, it should not seem surprising when Wigner proposes in “Two Kinds of Reality”

(1964) that we should take the content of conscious (sense impression) as the primary

reality rather than physical objects, very similar to the positivist’s account of ‘givens’, as

the only legitimate source of knowledge. In his opinion, positing the physical objects is

beneficial for connection of these contents. Interestingly, when he supposes the sensual

impressions as the primary reality, it sounds reasonable that his next stance will be the

skeptism about other conscious creature’s content; that is solipsism. He says:

“[The reduction of the wave packet] takes place whenever the result of an observation

enters the consciousness of the observer – or, to be even more painfully precise, my

consciousness, since I am the only observer, all other people being only subjects of my

observation”(Wigner,1964, p249)

Although in his final papers he has some desire for getting away from this kind of

solipsism, he finds it very difficult (Primas, 1995, p11). As we’ll see later, this solipsism

works against the Wigner’s Friend Paradox.

Moreover, positivism faces many problems such as setting up verification rule

definition and being too narrow in result such that even scientific laws cannot be

considered as verifiable and also the verification rule itself.

PS2:

Attribution of wave function (or a state) to knowledge (or information) rather than an

objective entity needs more clarification. First, it should be made clear that it is related to

the knowledge of what? Of the real nature or of our impressions? With his positivistic

attitudes he thinks the wave function has only epistemic value of the probabilistic relations

among our impressions. Second, if we can propose a measurement process for information

then this knowledge can be realized through this ‘information’ according to PS1 and can

be taken as a member of our existents set; albeit a positivistic existence, since this

realization does not necessitate any metaphysical postulation in this framework.

This pre-supposition can be interpreted as the completeness claim about QM. Since, it

has been stated in PS2 “for each entity” which covers all entities and also “all the related

knowledge” which encompass the totality of our knowledge. Thus let’s present PS2 in the

following way:

PS2*. QM is a complete true physical theory.

What precisely ‘complete’ and ‘true’ mean is itself a long story. We can be content

with these declaration that complete is to be able to explain every phenomena (entities)

which has an empirical evidence and for truth is to be at least empirically adequate.

There are some objections to this supposition. One is against to this claim that the

wave function describes the system in its most complete (possible) way. For instance, it

is claimed that “it is impossible in principle to determine a pure state experimentally” (

Primas, 1995, p15). Thus the pure mathematically constructed state is not practically

available and in consequence no such wave function is experimentally accessible from

which all the knowledge can be withdrawn. In addition, there are some empirical

evidences around wave function which makes it somehow different from mere epistemic

such as the wave interference patterns in two slits experiment. For the sake of explanation

of this observable (and measurable) phenomenon it is helpful to posit something more

than mere knowledge for the interpretation of the wave function. That is taking a wave-

like account of this quantum being has explanatory power. Thus we explanatorily lose

something if we reduce wave-function to mere epistemic interpretation.

PS3.

In this pre-supposition Wigner posits that the information gained by one observer is

communicable with others. In this way, we can call it observer-independent and thus it

gains an objective meaning. Although to clear up this objectivity it’s better to use Searle

(1980) literature in which he distinguishes between epistemic objectivity and ontological

objectivity. The latter is the well known objectivity which ontologically there is an object

which its existence is independent of our minds but the point is that the object of interest

(or the entity) is not subjective and the entity for its existence does not rely on our mind.

In this way it is mind independent. However, in the former, we have the mind-

independence but not ontologically; that is the entity is subjective and in its existence it is

relies on our mind and in contrast to the latter it cannot be existed without mind. But its

objectivity lies in being independent of one’s ideas or theories of special epistemic or

cognitive attitude which leads Searle to call it epistemic objectivity; such as consciousness

which independent of our conceptual and theoretical system can be claimed to exist ,

although not ontologically independent of our mind.

One other way of titling this type of objectivity is to call it “inter-subjectivity” which

means to be common in all subjects though ontologically subjective. Wigner pre-supposes

the inter-subjectivity of the observed information from the wave function (or state);

although it will be explained later that his paradox is aiming this pre-supposition!

PS4:

This pre-supposition is an epistemic interpretation of probabilities and also wave-

function. That is wave-function is attributed to knowledge and probabilities is our

expectation of this knowledge evolving. This plus PS1 accomplish the positivistic account.

There is also another pre-supposition which is mentioned by Bass (1971, p58) and also

D’ Espagnat (2005, p1950).

PS5. There exist at least two independent conscious minds.

This assumption is necessary for inter-subjectivity and also PS3. Since, if there is only

one mind, that is my own, how communication or sharing of information or subjectively,

i.e. inter-subjectivity, can become possible. Moreover, it is necessary for the argument.

For we need at least two conscious minds there: one is the observer’s mind (friend) and

the other is our own to ask what the result of observation was.

The first obvious problem with this assumption is that it can be considered to be in

contrast with PS1. As we saw, PS1 can be interpreted to ends in solipsism (as Wigner his

own comes close to this conclusion) while PS5 clearly denies it. One way to bypass this

problem may seem to be purely positivistic and assert that it is meaningless to entail or

state any metaphysical proposition like existential claims which cannot be verified.

Therefore it is not eligible to say anything about existence of one or more minds and only

stay faithful to our perceived impressions. However, as mentioned, there are a couple of

problems with classic positivism mainly in ‘verification’ definition

Now it is the time to restate the paradox in a way that Wigner his own has stated it, of

course, with some more analytical formulation.

The Paradox

Let’s suppose that there is a flash event (or object) to be observed which has two

states: φ ( ),φ ( ) . Furthermore, there is an observer (Wigner’s friend)

who has two states after interaction (of observation process):( : ? ) , (in

which ). Then we have the mixed status of the

object plus the observer after observation when it has flashed and the observer is a state

that answers ‘Yes’ to our question:φ ∗ X and another when it has not flashed and the

observer answers ‘No’ to our question which is: φ ∗ X . Now suppose that the observation

has been made by the observer and then, according to QM, before we ask him and know

his answer, we have

P1. The state of the observer plus object system, after the observation and before

hearing his answer is:

(1) α(φ ∗ X ) + β (φ ∗ X ); that is the state is undetermined.

in which |α| is the probability of Wigner’s friend answering ‘Yes’ to our question

and |β| answering ‘No’.

Now, if after the friend’s observation, we ask him:

"What did you feel about the flash before I asked you?" he will answer, "I told you already, Idid [did not] see a flash," as the case maybe. In other words, the question whether he did or didnot see the flash was already decided in his mind, before I asked him”(Wigner, 1967, p180)

Thus we have:

P2. The state of observer plus object system, after the observation and before hearing

his answer is:(φ ∗ X ); that is the state is determined.

Therefore, there is an obvious conflict between P1 and P2. So it is a Paradox.

According to Wigner, if we replace the observer with an instrument nothing paradoxical

will arise. Since, unless someone (conscious one) makes the observation (or reaction) it

can be claimed that the state of the system is undetermined and so P2 is False.

What is the legitimate conclusion of the paradox?

Let’ suppose that the inference, specially the phrase that has been quoted from

Wigner in the paradox description, is acceptable. Now what can be deduced legitimately

from the paradox? It is well known to take consciousness responsible for the collapse a

conclusion of this paradox. As we stated before, Wigner intends to illustrate the causal

effect of consciousness by this argument. Let’s see how successful he is.

To get rid of the paradox, it is better at the first stance to go through the pre-

suppositions. There should be something wrong with them. The pre-supposition which

Wigner himself target is PS2; mostly the completeness of QM; PS2*. By this rejection he

has deduced two kinds of incompleteness and has gained two results:

C1- The incompleteness of QM about explanation of a conscious being as an

entity:

“ It follows that the being with a consciousness must have a different role in quantum

mechanics than the inanimate measuring device.”(Wigner, 1967, p181)

Analytically he claims that P1 cannot be supposed. Thus in his view P1 is false. That

is we cannot assume a superposition state for the consciousness being in agreement with

QM explanatory system. Then since we have used PS2 for inferring P1, we should reject

PS2. For we have supposed that QM explanation does include ”all the knowledge” for

“each entity” and thus it should encompass the conscious being too. Therefore, we should

modify PS6 in this way that QM cannot explain conscious being’s phenomenological

behavior and so we should treat it differently (“have a different role”).

However, rejection of PS2, entails in two different statements. One is the conclusion

that we cannot attribute wave-function to consciousness. In other words, it cannot be

considered in QM explanatory domain at all. If we claim in this way, it means that QM

has nothing at all to describe it. It seems in contrast to PS4 due to which QM tells

something about the expectation of our conscious experience (or impression). And also in

contrast to this positivistic assumption that wave-function is about knowledge which is a

conscious natured entity. The second conclusion out of rejection of PS2 is that it does not

include all the knowledge but some. It sounds more reasonable in Wigner’s framework.

Another incompleteness claim is:

C2- QM is incomplete in its principles, especially about the collapse.

We may add the following statement as a principle or an extension of the

collapse principle : ‘After the observation of any conscious being, state of a system

should be supposed reduced. ‘Accordingly, P1 turns out to be false.

It is important to insist that supposing a causal role for consciousness is not included

in any of these implications. What can be inferred from the first one is only that we

should treat conscious being differently. To be different does not mean to be a cause of

anything like collapse. To have a different role does not necessarily mean to have a

causal role. We can only infer that some of its behavior cannot be explained by QM.

Therefore, the first implication of the paradox does not bring anything new for the

collapse explanation. The only legitimate and also fruitful implication is the second one

which I think with some modifications is the main logical conclusion of the paradox. In

other words, what the paradox targets is for after the collapse and not at the collapse.

After the collapse, we have a piece of knowledge of a conscious being which should be

treated differently. This different treatment is not sufficient to claim that it is the

consciousness which is responsible for or cause of collapse. That is only inferring that we

are not permitted to attribute a quantum superposition state to it.

Moreover, in PS3 words, it is communicable or transferrable. It can be used

empirically true, by other conscious beings. To me the paradox is only a new

representation of PS3. It attempts to show that how it is paradoxical if a conscious one’s

observation (information or knowledge) cannot be supposed to be used (explanatorily) by

another conscious being; i.e. how it is paradoxical if supposed incommunicable. It may

be inferred that the paradox is trivial since it is restating its presupposition. However, to

Save the paradox, I think that we can take PS3 out of the presuppositions, since it has not

been used in the deduction process and rather the argument is designed to show how

paradoxical it is if we reject it.

To illustrate this claim more analytically, let’s eliminate the PS3 and reformulate the

paradox in the following way:

Pre-suppositions:

PS1: Existence definition

PS2: QM completeness

PS4: Taking probability as a subjective expectation of given impressions

PS5: Existence of at least two conscious beings

Premises:

P1: superposition state: the state is undetermined (which is true according to PS2)

P2: Determined state (which is true intuitively)

-------------------------------------

Contradiction (P1 & 2 cannot be True)

What is assumed here, without PS3, is that P2 is taken intuitively true. However, with

PS3 assumption, we could deduce P2 from it. Now, resolving of the paradox comes as

follows: P1 and P2 cannot both be simultaneously true. Thus one of them should be false.

Rejecting PS2 entails in rejecting P1. So P2 should be true. P2 means PS3. That is the

communicability.

Now, since the conscious report is only a subjective impression, it means that this

subjective knowledge can be transferred to another subject. This is the ‘inter-subjectivity’

which was discussed before on analysis of PS3.

As we stated, attributing a causal role to consciousness at collapse cannot be deduced

from those two implications stated above. However, there may still be a route to this

claim. There can be a more modest claim that the conclusion of the paradox is the answer

to the query about where and when the collapse happens. (Albert, 1994)

Let’s see how it makes sense. According to the paradox, if we substitute a conscious

observer with a measuring device, we do not encounter a conflict. Since, according to

Wigner, P2 cannot be true in this case. That is, the state will not be reduced in a non-

conscious case. It means that the measuring device does not reduce to any eigenstate

unless some conscious one goes and observes it. Then if we accept this, we will have a

coincidence of a conscious presence and collapse; therefore we can conceive a kind of

causality or at least correlation between them. However, to say that there is no collapse in

non-conscious measurement cannot be the conclusion of the argument. It seems that we

should take it as another pre-supposition. Since, it is used in the paradox, when Wigner

claims that P2 cannot be true even after interaction. Therefore we should add the

following pre-supposition to our set:

PS6. Collapse happens only at the presence of a conscious being.

By which the paradox will not arise in a non-conscious case. However, it is not

illogical to deny PS6. It is legitimate to say that the system has collapsed after the

interaction by measuring device (as coherence theory states). So the paradox still works

in non-conscious cases. To save the paradox, we can claim that its related knowledge is

not communicable. However, if we want to be faithful to the positivistic PS1, this claim

cannot be verified and we should remain silent either positively or negatively. Thus the

supposition of PS6 is necessary to have any claim about non-conscious cases. As we said,

there is an important point about getting it as a pre-supposition. It cannot be deduced

from the paradox and so cannot be the conclusion of it. Again, we are unable to take the

causal role out of it.

It is worth noting that PS6 can be stated in this way: ‘Collapse is known to happen

only at the presence of a conscious being’. Which is trivial; since, everything can be

known only at the presence of a knower. Furthermore, PS6 needs a clear distinction

between conscious and non-conscious, which will be discussed later. However, taking

PS6 away, means that collapse happens for all measuring observers, either conscious or

non-conscious, and thus paradox works for both categories. And by this way, Wigner

loses the privilege of conscious beings. Therefore, he should keep this pre-supposition.

In sum, supposing a causal role for conscious being cannot be the legitimate

conclusion of the paradox and cannot be inferred from it, rather the communicability of

collapse knowledge is one of conclusions and also the incompleteness of QM.

Evaluation of the inference

Supposing that all pre-suppositions are acceptable, let’s take a more precise look over

the inference. It seems that the heart of paradox is in the question quoted on the paradox

part; when we ask from the observer what he has observed before we ask him, he answers

I told you I saw a flash. From this, Wigner deduces, since it is strange to conceive the state

of the observer remains undetermined after the observation, P2 is true and so the paradox

will arise. To Wigner it seems as an intuition which can go under question. This intuition

is another version of PS3 due to which the observation (information) of one observer can

be used by another. However, Wigner could state the paradox in this way that P2 is true on

behalf of PS3. Thus it will be no more intuitive inference. But P2 has nothing more than

PS3 or in another word it is a special and practical case of PS3. It seems as an ad hoc to

take intuition from premise to presupposition. Actually we have again intuition is the basis

of the inference. If someone rejects this intuition, there will be nothing logically false. To

leave out the intuition is not so bizarre for QM; frankly, there are many things strange

there. In McFarlane words, Wigner has objectifies something subjective (experience or

knowledge of his friend) and there is no way to be sure that his friend is conscious about

something. This may entail the solipsism which Wigner himself was worried about

(McFarlane, 1998, p10). In sum, the objection is that Wigner has based his inference on

an intuition which can set in doubt. However, since it has been presupposed in PS3,

logically there is nothing wrong with the inference, but it seems ad hoc. However,

rejection of PS3 is another way of resolving the paradox which will be discussed in next

part.

There is also another formulation of this paradox proposed by Albert and Putnam

(1995) which reveals some interesting points around incompleteness of QM. In brief, the

key idea is that getting (1) as a state of a system ( with α=β=1/√2), since according to

quantum mechanics every quantum state of a system is an eigenstate of an observable, we

can assign an observable O which (1) is its eigenstate with eigenvalue (for instance) +1.

Then, in place of supposing someone to ask Wigner’s friend, we can suppose an additional

observer who measures the O and informs him about observation result of O and form a

new state:

(4) α{ X and he is informed that O measurement is +1}*φ +β {X and he is informed

that O measurement is +1}*φNow, again with similar reasoning made to form O, we can assume 4 as an eigenstate

of an observable O* with eigenvalue +1. There is also a T which is attributed to the

knowledge of the friend (first observer) which is +1 when his state is X1 and is -1 when his

state is X2.

The first important implication here is that Wigner’s friend is the only observer who

can be both aware of two incompatible observables T and O* simultaneously. As we will

see this is the main origin of the problem.

Then let’s assume an observable O' in the following way:

(5) {O'=1} = f { X and he is informed that O measurement is +1}*φ + g {X and he

is informed that O measurement is +1}*φ

{O'= -1} = f {X and he is informed that O measurement is +1}*φ - g {X and he

is informed that O measurement is +1}*φNow suppose that f≠g and f or g≠0 and for instance T= -1; that is the Wigner’s friend

is in X2 state. Then given the initial values of T and O* when we want to set the

probabilities of O' measurement outcomes the problem arises; to establish a quantum state

which expresses all what Wigner’s friend knows to be true (which is needed for setting the

outcomes of O') is not possible in standard formulation of quantum mechanics. “..because

…each one of the two quantum-mechanically incompatible things [he] knows [T and

O*]… justifies the ascription of a different q-state to that composite system; and those two

states entail different and incompatible probability distributionsover the various possible

outcomes of anupcoming O'-measurement.” (Albert and Putnam, 1995, p5)

Now we have the same implication that Wigner made at C1, the incompleteness of

QM about explanation of some aspects of conscious observation. However, in addition to

the more precise inference and less intuitive way of this new formulation, it has cleared up

the incompleteness claim. In Wigner’s claim, the different role of conscious entity or

consciousness is not so clear and is too general. However, here we have something more

specific: incompleteness about a (specific)subjective knowledge and not consciousness in

general. Thus the claim is about the knowledge. Moreover, it has brought up another

interesting implication which is something new about the incompleteness of QM:

C3. QM is incomplete in two quantum mechanical incompatible observable value

attribution.

According to Albert and Putnam, QM has not been designed to cover these cases. And

this is the origin of the paradox. C3 can also be considered as an explanation of T1 that

why the conscious observer should be treated differently.

Other Solutions for the Paradox

There are also other solutions for the paradox which one them is to reject PS5. It is

proposed by Bass and McFarlane. The claim is that there are not two independent

conscious minds and thus we have only one. Accordingly, in the paradox, Wigner’s friend

and the asking observer are not two independent conscious beings and the paradox will

not arise. We can understand this resolving in different manners. First is solipsism, that is

to reject any conscious entity (Wigner’s friend) other than me. It’s the very idealism. Due

to this, P2 is not true and the sate of my friend will not be determined unless, I go and ask

the imagined my mind-dependent friend. However, even assuming this is true, I think the

paradox can be presented in the knowledge levels of that single ‘me’. Suppose I am the

only conscious entity and I pursuit the paradox experiment. There are still some piece of

knowledge for me (knowledge about status of my (so called) friend before I ask him)

which still cannot be explained in QM. Thus the paradoxical point remains still about the

knowledge. The other way is to suppose a single mind, in an ancient orient discipline such

as Vedanta (Bass, 1971) or as Berkeley, which every conscious entity is a limited version

of it, thus it is conceivable that two different conscious entities can be in some level united

to share knowledge. However, metaphysically positing this being ends in many problems,

especially of non-conscious beings, objectivity definition, causality and undetermined

nature of reality.

There is also another solution to the paradox which is proposed by De Espagnat. He

suggests a level of inter-subjectivity named “Co-emergence” which, even in a positivistic

sensual ‘given’ space, it can be considered as a predictive empirical mind-independent

reality. That is determined realm. Similar to Broglie–Bohm theory in which particles can

have positions but still posses quantumic behavior by the effect of pilot-waves, he

suggests a new model in which we can consider a conscious being (like Wigenr’s friend)

to be in a particular state but still remains in a quantum descriptive framework. In this

way, he resolves the paradox. To have both a determined state and an undetermined

quantumic behavior. Moreover, he uses this analogy reversely, that is from the paradox to

particles, and proposes to assign “internal states of consciousness“ for particles which are

hidden (but to themselves) and not predictive. Then, by getting help from decoherence

theory, he attempts to illustrate that when it comes to a macroscopic level we can suppose

an inter-subjective level in conscious states which can be predictive and also empirically

mind-independent real; that is every conscious state in the world will tend to same state;

though “presumably lies beyond our inter-subjective abilities at describing” (De

Espagnent, 2005, p 1955 ).

First, this suggestion, as decoherence theory itself, needs a clear definition of

macroscopic vs. microscopic which is very hard to reach. Second, the analogy seems

qualitative and should be presented in more precise quantitative way. For instance, how is

this quantumic behavior for macroscopic conscious level? Could we assign a

superposition state in the paradox? Is P1 true, accordingly?

General Objections

Even accepting the conclusions made by Wigner, There are still some other objections.

First is the criterion for distinguishing conscious out of non- conscious. “What the theory

predicts hinge on the precise meaning of the word conscious” (Albert, 1994, p82) which

is not available. Although one answer is that all the entities are conscious, such as the way

De Spagnat attributes internal consciousness to every particle, which as stated before,

needs more clarification.

Assuming we have this criterion, the other objection is about the collapse in non-

conscious cases like in nature at the absence of any conscious being. How is it possible?

Should Wigner deny this kind of collapse? That means all the states of the universe

systems remains undetermined till a conscious being make an observation (PS6). This

entails in a sort of idealism..

Another objection which has been stated mainly by Wigner himself is that the paradox

is constructed over QM which we are not sure about its truth. If it goes wrong, the

paradox will fail. For instance, P1 cannot be asserted. If he means that QM is not totally

true, this objection may work. However, if he means that it is incomplete, it cannot be the

case, since he has used it as a pre-supposition (PS7).

Conclusion

By contemplating “Wigner’s Friend” paradox, we concluded that he is not successful

in using it for illustrating the causal role of consciousness in the collapse. The paradox is

mainly entails in communicability of conscious observation (knowledge) and it seems as a

new presentation of PS3. Saving the paradox from triviality, I think that we can take out

PS3 out of the presuppositions, since it has not been used in the deduction process and

rather the argument is designed to show how paradoxical it is if we reject it. Resolving the

paradox, results in three implications made over refusing the completeness pre-supposition

(PS2*). First, we should treat differently the conscious related (observation) event in QM.

This can be made more clarified in Albert and Putnam proposal to set this conscious state

as knowledge (or information). Second, is incompleteness in collapse principle which

entails to add the following statement: “After the observation of any conscious being, state

of a system should be supposed reduced”. It is more precise to say that this may results in

PS3 either. Thus, if we take out PS3 and resolve the paradox by rejecting PS2, by one of

our interpretations of QM incompleteness, we can conclude PS3. Third is the

incompleteness of QM in two quantum mechanical incompatible observable value

attribution which seems to be the origin of the paradox.

In evaluation of pre-suppositions we discover two other premises: PS5, that is there

exist at least two conscious minds and PS6, that is collapse only happens at the presense of

a conscious mind.

Let’s add this point that logically, I think that PS1 and PS4 are not necessary for the

paradox inference and therefore one can set up the argument without necessarily these

positivistic assumptions. Thus the argument can be :

Pre-suppositions:

PS2: QM completeness

PS5: Existence of at least two conscious minds

PS6: Collapse happens only at the presence of a conscious mind

Premises:

P1: superposition state: the state is undetermined (which is true according to PS2)

P2: Determined state (which is true intuitively)

-------------------------------------

Contradiction (P1 & 2 cannot be True)

In another version, we can add PS3 which can be mentioned as a support of the P2,

which makes some implications (communicability) trivial.

Finally, the inter-subjectivity of which the paradox gives an insight worth more clear

investigations and it seems fruitful in our metaphysical interpretations of both ontological

and also epistemic problems over QM and also philosophy of mind.

References

1) E. P. Wigner, Remarks on the Mind-Body Question, Symmetries and Reflections, IndianaUniversity Press, Bloomington, pp. 171-84, 1967

2) Bernard d’Espagnat, Consciousness and the Wigner’s Friend Problem, Foundations of Physics,Vol. 35, No. 12, 2005

3) E.P. Wigner, Two kinds of Relaity, The monist, Vol. 48, No. 2, Philosophical Implications of RecentDevelopment in the Sciences, pp. 248-264, 1964

4) H. Primas and M. Esfield, A Critical Review of Wigner’s Work on the Conceptual Foundation ofQuantum Theory, philsci-archive.pitt.edu/1574, 1997

5) J.R. Searle, Minds, Brains, and Programs, Behavioral and Brain Sciences, 417-457, 1980

6) David Albert, Quantum Mechanics and Experience, Harvard University Press, 1994

7) Thomas J. McFarlane, Conscious and Quantum Mechanics, www.integralscience.org, 19988) David Albert and Hilary Putnam, Further adventures of Wigner’s Friend, Kluwer Academic

Publishers, Topoi 14: 17-22, 1995

9) Ludvik Bass, The Mind of Wigner’s Friend, Hermathena, No. 112, Trinity College Dublin, pp.

52-68, 1971