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Today this argument against the existence of an omniscient being occurred to me. Can someone point out the flaws? Can someone point me to writings about arguments like this one?

  1. If an omniscient being exists, there exists knowledge about the location and momentum of every particle in the universe.

  2. When Young's classic double-slit experiment is performed, an interference pattern is produced.

  3. This indicates that no knowledge exists about the path the photons take.

  4. Therefore, an omniscient being does not exist.

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    If no knowledge exists about something whether it be what a quantum system is doing or what I might choose to do next, then there is nothing for the omniscient being to know.
    – Frank Hubeny
    Jul 1, 2018 at 20:09
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    I think for our purposes this definition of omniscience will do: The state of knowing everything. To disprove omniscience, one needs to show one thing that is not known. In my argument, I point out that what is not known is is the path the photons take when there is an interference pattern. If the path were known, there would be no interference pattern.
    – lassic81
    Jul 1, 2018 at 20:09
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    The problem then is to define everything. Are all ypur fantasies a part of everything? E.g. knowing laws of physics in your dreams is a part of omniscience, right?
    – rus9384
    Jul 1, 2018 at 22:51
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    I don't see how 2 implies 3. Yes, there is interference. It merely means such wavy probability function. Yet, if these probabilities are pseudo random, 3 is wrong.
    – rus9384
    Jul 2, 2018 at 0:49
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    In Young's experiment, photons are fired through two slits, producing an interference pattern on a screen. When sensors are placed on the slits to see which slit each photon travels through, the interference pattern disappears. When we learn which slit the photons pass through, the interference pattern disappears. The reasoning from step 2 to step 3 is that an interference pattern exists only when the path the photons take is not known.
    – lassic81
    Jul 2, 2018 at 5:34

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To make sure one isn't setting up a straw man argument, that is, making up an opponent's position so it can be easily refuted, one has to find out what theists actually mean by "omniscience". The theist must define this, not the atheist. Given a quotable definition, the atheist can then try to find a logical flaw with that definition.

Wikipedia provides a basic definition that can be used as a starting point:

Omniscience...mainly in religion, is the capacity to know everything that there is to know.

To get more specific, William Lane Craig, a theistic philosopher, defines omniscience in "#164 The Trinity and God’s Omni- Attributes" as

The property of omniscience is the property of knowing that p, for any true proposition p, and not believing not-p, or, in other words, the property of knowing only and all true propositions.

Consider the atheistic argument presented by the OP:

  1. If an omniscient being exists, there exists knowledge about the location and momentum of every particle in the universe.
  2. When Young's classic double-slit experiment is performed, an interference pattern is produced.
  3. This indicates that no knowledge exists about the path the photons take.
  4. Therefore, an omniscient being does not exist.

Clearly there is a conflict between premises 1 and 3. In premise 1 there exists knowledge about the behavior of a photon that does not exist in premise 3. However, there is no quote from a theist justifying that premise 1 is what theists actually believe. This raises the possibility that premise 1 is set up to attack a straw man.

Consider the general Wikipedia definition of "omniscience" as "the capacity to know everything that there is to know". Note that premise 3 states "that no knowledge exists about the path the photons take". By this definition, one should not expect an omniscient being to know something for which "no knowledge exists". There is nothing there to know.

To get more specific, consider the definition Craig provided. Does there exist a true proposition about "the path the photons take"? According to premise 3 "no knowledge exists", that is, no such propositions exist. According to Craig's definition of omniscience there is also no contradiction.

This is not to say that some theists don't have definitions of omniscience that lead to a contradiction when coupled with premise 3. They might. However, the definitions from Wikipedia and Craig show that they can easily avoid this contradiction.

The OP has a further question:

Can someone point me to writings about arguments like this one?

The logical problem of evil presents something similar. The existence of evil given an omniscient, omnipotent and omni-benevolent God was claimed to be contradictory. Alvin Plantinga provided his "Free Will Defense" to resolve that apparent logical contradiction.

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    +1. Nice, analytical answer as usual.
    – Geoffrey Thomas ♦
    Jul 2, 2018 at 8:56
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    -1. It is not obvious whether the OP has religious omniscience in mind. He might just as well wonder about philosophical omniscience in the sense of Laplace's daemon (which is omniscient but impotent). The fathers of QM wanted philosophers to ponder its consequences, just like todays CS luminaries want philosophers to care about the consequences of computational complexity. Of course, philosophers are free to ignore those wishes, but attacking those wishes as "straw man arguments" is a bit more than merely ignoring them.
    – Thomas Klimpel
    Jul 3, 2018 at 11:30
  • @ThomasKlimpel Regardless of whether the argument refers to a religious or non-religious omniscience premise 1, given the version of QM in premise 3, is false. Who's definition of omniscience, religious or non-religious, leads to that false premise? The argument only applies to those people who have such a definition of omniscience, if any exist. However, the conclusion is general: an omniscient being does not exist. It needs to claim, "an omniscient being defined by the philosophy of so-and-so does not exist" to avoid the objection that it is a straw man argument.
    – Frank Hubeny
    Jul 3, 2018 at 13:04
  • Plantiga's argument requires defining free will the libertarian/idealistic/mystical way, which to be fair seems even more contradictory than OP's example (that could instead just be shunned by saying QM isn't really 100% settled for good). Anyway, I think incompatible-properties argument is the more generalized name of what he wanted. Put aside the plenty of ways omniscience clashes with physics (having ≥bits than the whole universe is tricky I guess), it may even conflict with God's own attributes.
    – mirh
    Jul 11, 2019 at 19:35
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    It is not logically impossible to observe the path of the photon in the double slit experiment, so the premise of this answer, that this is a logical impossibility, is incorrect. We HUMANS can do this observation. When we do -- it disturbs the interference pattern -- the waveform collapses when the observation is made, and then there is no more waveform to do the interfering. What this shows is that an omniscient God cannot be doing omniscience at all times -- omniscience must be discretionary, and generally withheld, or else QM would not work. . .
    – Dcleve
    Dec 21, 2020 at 19:53
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According to Copenhagen interpretation of quantum mechanics there is no particle state where the particle has simultanenously both a precise position and a precise momentum. The point is not that we do not know them. The point is that they do not exist simultaneously. Also an omniscient being cannot know a property which does not exist.

Hence your first statement does not seem correct to me.

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The answer by Frank Hubery is a good one, and he is careful to allow the theist position to speak for itself. However, his conclusion appears to me to be wrong, since he smuggles in an additional requirement for omniscience that is absent from the definition he quotes. According to the definition quoted in that answer, "omniscience" is defined as follows (emphasis added):

The property of omniscience is the property of knowing that p, for any true proposition p, and not believing not-p, or, in other words, the property of knowing only and all true propositions.

This definition posits omniscience as requiring knowledge of any true proposition p. This is a purely metaphysical requirement; it does not impose an epistemological requirement that p be "knowable", only that p be true. Hence, by implication, all true propositions must be known (by the omniscient being) and hence, all true propositions are knowable. The logical argument for this is as follows:

  1. (Definition) "Omniscience" requires knowledge of all true propositions;
  2. (Premise) There exists an omniscient being;
  3. (Implication) Every true proposition is known to some being (the omniscient being);
  4. (Implication) Every true proposition is knowable (at least to an omniscient being).

Hence, we see that under this definition of omniscience, if one believes that an omniscient being exists, one must deny the possibility of any category of true proposition that is unknowable. Now, it is of course open to the theist to change the above definition to preclude this (e.g., by positing that omniscience is knowledge of any true and knowable proposition p, plus not believing not-p), and thereby propose a weaker form of "omniscience". However, based on the above definition, that has not been done.

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    +1 By Craig's definition, omniscience is "the property of knowing that p" for any true proposition p. If the omniscient being knows the truth value of p, it is not only true but also knowable to that being. From the perspective of this omniscient being why would the category of true propositions that are unknowable not be empty? Where I am puzzled with Craig is he restricts omniscience to "propositions" with truth values. What about "knowing" how something feels that is not a true-false proposition?
    – Frank Hubeny
    Jul 3, 2018 at 1:13
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    By my reading of the definition used here, the category of true propositions that are unknowable would be empty, which is the point of the syllogism above. I understand "proposition" to refer to any truth-bearing statement, which would mean that all truth-bearing statements are knowable (at least to the omniscient being) within this viewpoint. I presume that this is the reason for the restriction.
    – Ben
    Jul 3, 2018 at 1:27
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Current ideas suggest this is definitely a possibility.

https://en.m.wikipedia.org/wiki/Superdeterminism gets round the issues of complete knowledge violating Bell's Inequality. It is not a widely held view in the physics world, but it is considered plausible.

The https://en.m.wikipedia.org/wiki/Universal_wavefunction suggests a fundamental unity to the state of the universe, that everything may derive from an initial single state and on some level still be entangled.

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  • +1 You've approached this by questioning premise 3 in the OPs argument.
    – Frank Hubeny
    Jul 2, 2018 at 15:02
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We need to not consider omniscience in isolation, but also with the qualities of omnipotence and being eternal to get a more complete picture of what these qualities imply.

Being eternal - or timeless - releases the entity from being contingent with regard to being able to "contain" future states. Since this entity is not bound to our mode of experiencing time - linearly - what is unknowable to us is not unknowable to it. It can move its frame forwards and backwards the way we can do this to a tape or even experience an integrated set of all frames concurrently - not bound to time. From here what is mutually excluded by the slit experiment from our frame of linear time is not excluded from the integrated (timeless) frame - even with a multiverse or Copenhagen interpretation of quantum mechanics.

So what are the implications with regard to what we subjectively experience as a sense of choosing from moment to moment - otherwise called free will?

Free will is purely subjective for any entity that is not THE ENTITY, and this subjectivity is persistent and convincing from our normal mode of waking consciousness. Other modes of thinking can be elicited through such means as sense deprivation, meditation and via drugs such as LSD, DMT and psilocybin. (We should not ignore these modes of thinking or dismiss them out of hand because they are part of the human experience and can be elicited rather easily with the right stimuli. I say that because philosophical discussion tends to operate within an almost purely logical-rational frame, and the human experience is not so tightly bound, and this is supported by neurological research and even the physical sciences. Kurt Godel reminds us not to be too dogmatic about our axioms and the castles we build upon them.)

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This is a valid argument, with caveats.

When the position and location of the photon in the double slit experiment is sampled, that collapses the waveform, and one no longer gets an interference pattern.

Humans can do this sampling, and when we do, we do not get the pattern. This is not a unique feature of the double slit experiment, but is true of many other aspects of Quantum Mechanics as well.

Therefore, if there is a deity who can sample the location data of QM particles, -- IE an omniscient deity -- that deity MUST NOT BE DOING SO! Your proof therefore does not disprove the existence of an omniscient deity, but instead disproves the exercise of that omniscience, other than as an occasional exception.

This disproof of active omniscience is more of a problem for panpsychism, which basically requires continuous omniscience, than it is for theists, who typically only expect occasional activity or awareness from God.

Whether God being only rarely aware makes any sense -- would potentially be subject to a further critique, but an anti-theist would have to do further work to argue that point.

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Your first premise assumes that there are particles, and that they have location and momentum, and that all this is knowable.

Buddhism is an example of an entire school of thinking that claims that all phenomena are empty of own-being, ie there are no things that have an intrinsic nature; rather all phenomena arise in dependence on other factors, which in turn depend on other factors, and so on, and so on. Hence, any alleged knowledge of things as they are is entirely illusory.

Likewise, Kant repudiates the possibility of knowledge of the Ding-an-Sich (the thing in itself).

So, to get your argument of the ground you first need to be able to establish that knowledge of particles and their characteristics is even possible. Omniscience is more or less a red herring in your scheme.

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This argument assumes that an omniscient being is limited by the constraints posed by the argument. If such a being isn't, one might as well be arguing who'd win at arm wrestling, God or Superman.

I'd be surprised if an omniscient being is limited by anything we barely evolved humans could conceive of, such a being would by definition transcend our primitive notions about the nature of existence.

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  • You raise a good point. The argument is only a "logical" argument to test if our concepts of what an "omniscient being" might be are contradictory or not. I don't think they are contradictory. What theists believe to be God hopefully goes far beyond these premises and conclusions.
    – Frank Hubeny
    Jul 3, 2018 at 4:46
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The flaw in your statements is in #3. This becomes clear if you keep track of who is doing the knowing (where the knowledge resides). Let me analyze and comment on each statement.

1 - This is a definition statement, and all knowledge resides in the omniscient being.
2 - This is a factual statement that relates to a specific human experiment.
3 - This statement represents a misunderstanding of the result of the mentioned experiment. There is (some) human knowledge of the path the photons take. But more importantly, even if humans had no knowledge of which path the photons take, by definition (statement 1), the omniscient being would know!

In other words, you are trying to put human limitations, on an omniscient being!
If statement 1 is true, then statement 3 is false, and vise versa.

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As others have pointed out, to answer this one would have to define omniscience, and how you choose to do it determines your answer to the question. (Personally I think that purported paradoxes about the deity are based on silly definitions of ‘omni-‘ predicates, which should really just be understood to mean very knowledgeable and very powerful etc. However acceptance of my view would involve shutting down a long-thriving cottage industry of debating consequences of these silly definitions.)

However it is true that in QM, while the quantum state itself evolves deterministically in time according to the Schrodinger equation, the observables representing the classically-appearing world are usually probabilistic and in any quantum state some will be maximally uncertain, and you will observe one of a (possibly infinite) number of values with a probability given by the Born rule, so you cannot have perfect (right every time) knowledge of their values. Whether you deem an entity which knows the quantum state of the universe and can evolve it according to the Schrodinger equation as being omniscient or not is a matter of definition.

A different point, which people may find interesting, is made by Jenann Ismael in her (excellent) book ‘How physics makes us free’. The point Ismael makes is easier to communicate by drawing a space time diagram than by writing, but roughly: if you pick a space time location L1 and another even an arbitrarily short way into the future at the same spatial location L2, the past light cone of L2 includes events not in the past light cone of L1. So it not possible, as a matter of physical law, for an entity at L1 to have all information in principle relevant to perfectly predicting the future at L2 (e.g. a stray photon could come in and interfere, and L1 could not possibly have known about it). So even if you could construct a Laplacian demon, it could not be located in the physical universe and have all the information needed to make its calculations.

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No. We need to use a stronger experiment, though. Consider the Stern-Gerlach device. Ions are sent down a tube, and a magnet at one end of the tube scatters each of the ions in one of two directions based on their spin. If the magnet is turned off, then the ions coalesce into a single group.

The nature of quantum measurement, combined with the Kochen-Specker theorem, implies that the ions are in a superposition while traveling down the tube, and are only collapsed due to the influence of the magnet at the end of the tube. As a result, no measurement of spin is occurring within the tube; there are no gods or demons able to measure the ions while they are still in superposition.

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