A Case Against Omniscience: Fallibility

An omniscient being is impossible as it is always possible that
it is mistaken in its belief that it is omniscient.

Citation Information

Allan, Leslie 2022. A Case Against Omniscience: Fallibility, URL = <>.

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DRAFT FOR REVIEW (draft release 9 August 2022)

1. Introduction

Many philosophers have given thought to the contradiction between God's omniscience and human beings' capacity to act freely. Other philosophers have written on the tensions between the notions of omniscience and knowledge itself. For example, Grim [1984, 2013: §§V–VII] argues that there is no set of all truths for God to know. Grim [1983: §§5–7, 1985, 2013: §§VIII–IX] and others [Wierenga 2021] also point out the problem of indexicals (How God cannot know what I know: that I am writing an essay, for example).

This essay constitutes one of three arguments about the impossibility of omniscience. For this essay, I present a case based on what it is to know something as opposed to merely believing something that is true. My other two arguments [Allan 2022b] are independent of the one presented here and draw attention to how knowing everything leads to an infinite regress.

Before I present the formal statement of my argument from fallibility, let me summarize the core of it in less formal terms. My argument basically hinges on the question: How would an omniscient being know that it is omniscient? Clearly, if it did not know infallibly that it is omniscient, then it is not, in fact, omniscient. For any being that thinks itself omniscient, it must face the possibility that it is being deceived by an evil demon or by being a brain in a vat or that it is suffering a delusion. However, this being has no conclusive reason for being infallibly certain that it is not mistaken in thinking itself omniscient. Therefore, it cannot be omniscient.

2. Formal Statement of the Argument

  1. For Being K, if K is omniscient, then K knows the truth value of every proposition.
  2. 'Being K is omniscient' is a proposition.
  3. If Being K is omniscient, then K knows that 'Being K is omniscient'.
  4. If Being K knows that 'Being K is omniscient', then, for Being K, there is no epistemically relevant reason for doubting that 'Being K is omniscient'.
  5. For Being K, there are epistemically relevant reasons for doubting that 'Being K is omniscient'.
  6. It is false that Being K knows that 'Being K is omniscient'.
  7. It is false that Being K is omniscient.

Now let Being K be a being that thinks itself God; that is, a being that thinks itself omnipotent, omniscient, omnibenevolent and immutable (or some other set of perfection-making attributes). From (7), then, this being that thinks itself God is not, in fact, omniscient. If omniscience is a necessary attribute of God (as per classical theism), then God cannot exist.

3. Support for Premises

(1) is analytically true.[1]

(2) is uncontroversial.

(3) follows logically from (1) and (2).

(4) is supported by the principle that 'X knows Y to be true' if and only if 'X has epistemically relevant reasons for believing Y and no epistemically relevant reasons for doubting Y'.

(5) is supported by the fact that it is logically possible that at least one proposition believed by K is false. Two scenarios in which K believes a false proposition are that K is a brain in a vat (see Putnam [1999]) being manipulated by other more powerful beings or is being deceived by Descartes' demon [Descartes 1641]. A third scenario is that K is experiencing delusions or some other serious mental dysfunction. This third scenario in fact plays out with persons suffering from psychosis. Some psychotic patients actually believe that they are God (see, for example, Moralis [2008: 260 and Rudalevičienė et al [2008])[2]. Note that the truth of (5) does not need to meet the stronger requirement that it is possible that an omniscient being is mistaken. It only needs to meet the weaker requirement that K cannot epistemically justify the proposition that it is impossible that it is a brain in a vat or is suffering delusions or some similar epistemic distortion.[3]

(6) modus tollens (denying the consequent) from (4) and (5).

(7) modus tollens (denying the consequent) from (3) and (6).

4. Reply to Objections

In this final section, I will deal with some objections that have been raised against my argument.

Objection 1: Premise (5) is false for the reason that doubt only arises for non-maximally great beings such as human beings. God, however, being maximally great is eternal, omniscient and omnipotent and as such is never unsure, never doubts and is never in a situation that allows for doubts to occur.

Reply: My response is that Premise (5) does not refer to God or to a maximally great being. In my argument, K ranges over the entities that exist. K picks out an unspecified individual in a class of entities. It serves the same function as 'some person' in the following sentence:

For some person, if that person is a policeman, then that person enforces the law.

My argument draws on the conditions for 'knowledge' itself; what it is for a being to 'know' some fact. For me to say that God is omnipotent, omniscient, omnibenevolent and immutable is acceptable as this statement is only defining the notion of 'God'. What my argument tries to show is that this notion of an omniscient God cannot be instantiated as it is self-defeating. This is akin to our seeming to understand the concept of a 'square circle'. However, by reflecting on the concept of a 'square circle', we realize that nothing can ever be a square circle.

The Meaning of Life: A Very Short Introduction by Terry Eagleton

Objection 2: Your argument is not really an argument against the existence of God. At best, it's an argument against God having the property of omniscience.

Reply: I agree that my argument is not an argument against the existence of every kind of conceived God. However, perfection in God's attributes has been seen as a necessary requirement by key religious thinkers through the ages, from Anselm to Aquinas to Descartes to most modern-day theologians of all stripes. Secondly, if God is not thought of as perfect in all his attributes, then it becomes more difficult to regard such a God as worshipworthy.

Objection 3: This is more an argument against a single unknown person than a god. I say that because you're assuming god is human-like in how they acquire, justify, doubt and understand knowledge.

Reply: This objection is similar to the first objection above. Let me answer it a different way. My argument is not an argument against any particular kind of knower. It applies to any kind of knower as it extrapolates from the conditions required for infallible knowledge per se. These conditions apply to any kind of human and non-human knower. Say members of an extraterrestrial species are able to 'know' the mental states of their fellow creatures through direct mind-reading. Say members of another species are able to 'know' the future through clairvoyance. Say members of yet another species are able to 'know' about far away objects through extra-sensory remote viewing. All of these examples are non-human ways of knowing. Yet my argument applies to all of these kinds of 'knowing' and knowing infallibly. My argument applies generally.

However God may think he knows, my argument applies. If the theist thinks there is a way for God to know that does not fall foul of my argument, then the onus is on the theist to show what that way of knowing is and how it avoids the force of my argument. Just to say that there is a way because that being is 'God' is simply special pleading. But even more importantly, for whatever posited way W the theist offers for God knowing that he is omniscient, the same question arises: How does God know, as for any being K, that he is not mistaken in his belief that he possesses means W for knowing infallibly. If the answer is that because he possesses that means, that answer only begs the question.


  • Allan, Leslie 2022a. Problems with God's Attributes, URL = <>.
  • Allan, Leslie 2022b. A Case Against Omniscience: Infinite Regress, URL = <>.
  • Duniho, Fergus 2019. The Impossibility of Omniscience, For the Love of Wisdom, URL = <> (Updated May 26, 2019).
  • Descartes, Réne 1641 (1972). Meditations on First Philosophy, in Descartes Philosophical Writings, trans. and ed. E. Anscombe and P.T. Geach, London: Thomas Nelson: 59–150.
  • Feldman, Richard 1981. Fallibilism and Knowing That One Knows, Philosophical Review 90/2: 266–82.
  • Grim, Patrick 1983. Some Neglected Problems of Omniscience, URL = <> American Philosophical Quarterly 20/3: 265–76.
  • Grim, Patrick 1984. There Is No Set of All Truths, URL = <> Analysis 44/4: 206–8.
  • Grim, Patrick 2013. Problems with Omniscience, in Debating Christian Theism, eds J. P. Moreland, C. V. Meister and K. A. Sweis, Oxford University Press: 169–180.
  • Kretzmann, Norman 1973. Omniscience and Immutability, in Philosophy of Religion: Selected Readings, eds W. L. Rowe and W. J. Wainwright, New York: Harcourt Brace Jovanovich: 60–70.
  • Malpass, Alex 2016. Craig's List – Omniscience and Actually Existing Infinities, UseOfReason, URL = <>.
  • Pearce, Jonathan M. S. 2013. God Cannot Know He Is Omniscient, A Tippling Philosopher, URL=<> (Retrieved: July 11, 2022).
  • Putnam, Hilary 1999. Brains in a Vat, in Skepticism: A Contemporary Reader, eds K. DeRose and T. Warfield, Oxford: Oxford University Press: 27–42.
  • Rudalevičienė, Palmira, Thomas Stompe, Andrius Narbekovas, Nijolė Raškauskienė and Robertas Bunevičius 2008. Are Religious Delusions Related to Religiosity in Schizophrenia?, Medicina 44/7: 529–35.
  • Wierenga, Edward 2021. Omniscience, The Stanford Encyclopedia of Philosophy, (Summer 2021 Edition), ed. Edward N. Zalta, URL = <>.


  1. [1] For alternate definitions of 'omniscience', see Wierenga [2021] and Grim [1983: §1]. These alternate definitions do not, I think, impact the force of my argument here.
  2. [2] Pearce [2013] has further suggestions for how K can be mistaken, such as that he may not be aware of another inaccessible dimension run by another God, that he is plugged into the Matrix and that he is part of an experiment programming him to think that he is omniscient.
  3. [3] For a discussion of the conditions under which agents know that they know and under which they don't know that they know, see Feldman [1981].

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