A Case Against Omniscience: Fallibility

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

Another way to state my argument in informal terms that may be helpful in grasping its logic intuitively is the following.

1. If Thinker X is omniscient, then Thinker X knows the truth of every true proposition.
2. If Thinker X is omniscient, then 'Thinker X is omniscient' is a true proposition.
3. If Thinker X is omniscient, then Thinker X knows that 'Thinker X is omniscient'.
4. If Thinker X knows that 'Thinker X is omniscient', then Thinker X has no epistemically relevant reasons for doubting that 'Thinker X is omniscient'.
5. For Thinker X, there are epistemically relevant reasons for doubting that 'Thinker X is omniscient'.
6. It is false that Thinker X knows that 'Thinker X is omniscient'.
7. It is false that Thinker X is omniscient.

Now let the term 'Thinker X' stand in for any thinker that thinks itself God. That is, let 'Thinker X' range over all thinkers that think itself omnipotent, omniscient, omnibenevolent and immutable (or some other set of perfection-making attributes). From premise (7), then, this thinker 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.

Support for Premises

(1) is true by definition.[1]

(2) is supported by the fact that if a thinker is omniscient, then a well-formed sentence ascribing omniscience to that thinker expresses a true proposition.

(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 Thinker X is false. Two scenarios in which Thinker X believes a false proposition are that Thinker X 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 Thinker X 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 thinker is mistaken. It only needs to meet the weaker requirement that Thinker X 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) follows logically from (4) and (5).

(7) follows logically from (3) and (6).

Copyright © 2022 Leslie Allan