A Case Against Omniscience: Fallibility

5. Replies to Basic Objections

In this section, I will deal with some basic objections that have been raised against my argument against omniscience and the existence of the God of classical theism. In the next sections, I will attend to some more sophisticated objections. Below is a complete list of objections considered.

Theology: A Very Short Introduction by David Ford

Objection 1: You have assumed that Thinker X is omniscient and then concluded that Thinker X is not omniscient. You have contradicted yourself.

Reply: Nowhere in my informal and formal presentations of my argument do I assume that Thinker X is omniscient. My premises (1) to (4) are conditional statements only. They say what is the case if Thinker X is omniscient.

Objection 2: If Thinker X is omniscient, then Thinker X knows that it is not a brain in a vat, deceived by Descartes' demon, and so on, in such a way that there would be no epistemically relevant reasons for doubting the proposition. None of these possibilities for error can apply to an omniscient being. As the source of all truth, it is God's basic intrinsic nature to know that he is omniscient.

Reply: Yes, it is true that for an omniscient being, it would not be in error about the truth of any of its beliefs. What my argument tries to show is that, in fact, omniscience is not possible. My argument applies generally to all knowing thinkers, demonstrating that no knowing thinker who thinks itself omniscient can be omniscient. By appealing to the possibility of there being an omniscient thinker, the objector has avoided considering my argument. This objection is akin to objecting to a demonstration that there can be no triangle with angles summing more than 180 degrees with the retort that the demonstration is valid only if there really is no triangle with angles summing more than 180 degrees.

Secondly, examine what it is to say that God's justification for him knowing that he is omniscient is constituted by his being the 'source of all truth'. If 'being the source of all truth' entails 'being omniscient', then the justification is question-begging and circular. To avoid this vicious circle, the classical theist could concede that 'being the source of all truth' does not entail 'being omniscient'. But then that leaves open the possibility for the source of all truth to not know that it is omniscient. In that case, it can't be omniscient.

Here is another way to approach the theist's bind. Say we come across a God-claimant and we ask him: 'How do you know you are really God?' And his answer is: 'I know I am God because I am God'. We then ask him: 'But how do you know the truth of the proposition that comes after the “because” in your justification?' He answers: 'I know I am God because I am God'. We are now in another vicious circle of 'justifications' that justify nothing.

Alternatively, to our initial question, the God-claimant could answer: 'It's in my basic nature to know I am God'. We then ask him: 'How do you know that you possess that basic nature?' He answers: 'Because I'm God'. We end up with the same question-begging and circular reasoning.

These kinds of thought experiments go beyond simply defining and conceptualizing an omniscient being and start to probe how omniscience looks instantiated in the real world. Considering these 'source of all truth' and 'basic nature' kinds of justifications, any intelligent being (including any God-claimant) with sufficient cognitive capacity is rationally compelled to conclude that, in the face of probing questions, simply insisting that one knows one really is God because one is God-like is entirely unconvincing, even to oneself.

Objection 3: Premise (5) is false for the reason that doubt only arises for imperfect beings, such as human beings. God, however, being maximally great/eternal/infinite/immaterial/omnipotent/the ground of being/necessary [insert favoured divine attribute] is never unsure, never doubts and is never in a situation that allows for doubts to occur.

Reply: My Premise (5) does not refer to God or to a being who is maximally great, eternal, infinite, immaterial, omnipotent, the ground of being or necessary. For Thinker X mentioned throughout the informal statement of my argument given in § 2, I ascribe none of the attributes of God named in the objection. My argument also makes no claim that one or more of these attributes is absent in God or in Thinker X. My argument applies to thinkers with or without one or a combination of these attributes. In my argument, Thinker X ranges over the set of thinkers who think itself God. 'Thinker X' picks out an unspecified thinker in a set of thinkers. It serves the same function as 'any person' in the following sentence:

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

That 'x' ranges over all thinkers that think itself God is again made explicit in the later formal presentations of my argument.

Note that, in particular, my argument draws on the conditions for 'knowledge' itself; what it is for a thinker to 'know' some fact. For me to specify in my argument 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 incompatible with the conditions required for knowing infallibly. Believing that an omniscient thinker exists is akin to trying to square a circle. Once one realizes that squareness is incompatible with circularity, one stops believing that there can be a square circle.

Atheism: A Very Short Introduction by Julian Baggini

So, 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 the possibility of knowing infallibly. My argument applies generally.

However the theist posits that God knows it is omniscient, 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 thinker is 'God' is simply a case of 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 this assumed God know, as for any Thinker X, that he is not mistaken in his belief that he possesses means W for knowing infallibly? If the answer is because he possesses that means, that answer only begs the question.

Objection 4: Your argument is not really an argument against the existence of God. At best, it's an argument against God having the attribute of omniscience.

Reply: I agree that my argument is not an argument against the existence of every kind of conceived God. My argument is particularly focused on the classical conception of God as a perfect being. However, perfection in attributes has been seen as a necessary requirement for divinity 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 5: You have presumed a particular definition of 'omniscience' that requires an omniscient thinker to know what it is not possible to know. The more reasonable definition of being 'all-knowing' is one that includes knowing only what it is logically possible to know.

Reply: This particular argument of mine does not show that it is logically impossible for a thinker to be 'all-knowing'. In contrast, my conclusion that it is impossible to be omniscient relies on what we know about knowledge. For example, my key premise (5) about reasons for doubt is not necessarily true. In any case, whether or not my argument demonstrates an internal contradiction at the heart of the notion of 'omniscience' itself, it does strike me as more than a little odd to admit, then, of an 'omniscient' being who recognizes it may be a brain in a vat, part of a scientific experiment by a higher being, suffering from the mental illness of psychosis, or labouring under some other epistemic error. This to me seems a pseudo-omniscience—a real wishy-washy omniscience—and very far from the 'perfect being' of classical theism.

Objection 6: For a thinker to know a proposition to be true does not mean that it must be capable of epistemically justifying the proposition.

Reply: This may be true of conscious beings with low cognitive ability, such as very young children and non-human sentient creatures. In a sense, we can say that a very young child and a giraffe 'know' that there is a tree in front of them simply on the basis that they are awake, looking towards the tree and their vision systems are not malfunctioning; that is, that they are standing in the right casual relation to the tree seen. In such a case, we do not require the very young child and the giraffe to give a verbalized reason for thinking that there is a tree before them. My argument, however, references thinkers who think themselves omniscient. Thinking that kind of thought requires a cognitive capacity that understands the concepts, at the least, of 'truth', 'know', 'reason' and 'justification'.

For such a thinker, if a belief in a proposition's truth cannot be justified, it is mere belief and not knowledge. The dominant theories of knowledge proposed by philosophers distinguish between such mere belief and knowledge using some criteria of epistemic justification. Without such reasonable grounds for believing, what warrant does any thinker capable of abstract conceptual thought have for claiming knowledge and not simply for some subjective feeling of conviction? For a thinker who thinks itself omniscient and is in fact omniscient, it must have a watertight reason for knowing itself to be omniscient. Otherwise, all it has is an ungrounded belief.

What will follow if we excuse the need for epistemic justification for a belief that one is omniscient? Well-known philosopher of religion, Alvin Plantinga [2000: 109], suggests just such an excuse when he writes:

Not even God himself, necessarily omniscient as he is, can give a noncircular argument for the reliability of his ways of forming beliefs. God himself is trapped inside the circle of his own ideas.

Here we have a solipsist God, on Plantinga's own admission 'trapped inside' his own thinking. This supposed God can't know then that his means of knowing is reliable, other than via his own internal reasoning.[10] This God is in no more an epistemically robust position than those psychotic patients occupying mental facilities who sincerely think they are God.

The upshot here is that if we do not require an omniscient thinker to have a justifiable reason for believing itself omniscient before we accept their claim to omniscience, we will be lumbered with a large surplus of omniscient beings. We will end up with one omniscient thinker for every psychotic patient who believes that they are God.

Objection 7: In order to support your case for premise (5), you presuppose that Thinker X is not omniscient. The truth of premise (5) entails that Thinker X is not omniscient. Since your conclusion (7) in your informal statement of your argument is that Thinker X is not omniscient, your argument is clearly begging the question.

Reply: My premise (5) does not entail my conclusion (7); that it is false that Thinker X is omniscient. Whichever method of proof you use, attempting to derive (7) from (5) results in an invalid argument. This is even clearer when considering the two formal statements of my argument.

To move from premise (5) to (7) in a formally valid argument, one needs to make explicit certain assumptions about omniscience and certain linking statements about the nature of knowledge. To move from (5) to (7), one needs additional premises. One needs my premises (1) and (2), from which to derive (3), and the addition of (4), from which one can derive (6) with the help of (5), and then from (3) and (6) one can derive (7), as I make explicit in the formal statements of my argument.

Furthermore, at no point in my support for premise (5) do I assert that Thinker X is not omniscient. At no point do I suppose or presuppose that Thinker X is not omniscient. My support for premise (5) is about the epistemic conditions required for a thinker to know itself to be omniscient. For the purposes of my support for premise (5), that thinker can be either omniscient or not omniscient. Revealing that it cannot possibly be omniscient is the work done in the other parts of my argument. For these reasons, my argument is not question-begging.


  1. [10] It may be thought that since Plantinga's God is 'necessarily omniscient', that this will allow God to escape from his solipsist world. It does not. On one reading of 'necessarily omniscient', God is necessarily omniscient in the same way that bachelors are necessarily unmarried and male. Such necessity is simply in virtue of the meanings of the words 'God' and 'bachelor'. This kind of logical/semantic necessity does not guarantee that God or bachelors exist. On the other hand, the Scholastics, taking a leaf from Aristotle's book, thought that each kind of being possessed its own 'essential' or 'necessary' attributes. However, even if we grant this sense of a 'necessary' attribute, it does not help the classical theist. Any being can only possess an attribute necessarily if that being, in fact, exists. If the being does not exist, there are no necessary attributes for it to possess. And my argument gives us reason to believe, in the case of God, that it is impossible for such a being to exist.

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