Omniscience is the capacity to know everything that can be known. In monotheism, this ability is typically attributed to God. It is typically contrasted with omnipotence. Omniscience is sometimes understood to also imply the capacity to know everything that will be.
This last point has been widely debated amongst theologians and philosophers because of how it relates to the problem of free will: If man is truly free to choose between different alternatives, it is very difficult to understand how God could know in advance which way he will choose. Various responses have been proposed (under the assumption that God exists, and is omniscient):
- God can know in advance what I will do, because free will is to be understood only as freedom from coercion, and anything further is an illusion.
- God can know in advance what I will do, even though free will in the fullest sense of the phrase does exist. God somehow has a "middle knowledge" - that is, knowledge of how free agents will act in any given circumstances.
- God cannot know in advance what I will do, and this is a limit to his omniscience. Omniscience should therefore be interpreted to mean "knowledge of everything that can be known".
- God stands outside time, and therefore can know everything free agents do, since he does not know these facts "in advance".
Omniscience is also studied in game theory, where it is not necessarily an advantageous quality if one's omniscience is a published fact. For example, in the game of chicken: two teenagers each drive a car towards the other. The first to swerve to avoid a collision loses. In such a game, the optimal outcome is to have your opponent swerve. The worst outcome is when nobody swerves. But if A knows that B is in fact omniscient, then A will simply decide to never swerve since he knows B will know his logical decision and B will be forced to swerve to avoid a collision. (this is assuming each player is logical and follows optimal strategy.)