The question of free will is whether, and in what sense, rational agents exercise control over their actions and decisions. Addressing this question requires understanding the relationship between freedom and cause, and determining whether the laws of nature are causally deterministic. The various philosophical positions taken differ on whether all events are determined or not — determinism versus indeterminism — and also on whether freedom can coexist with determinism or not — compatibilism versus incompatibilism. So, for instance, 'hard determinists' argue that the universe is deterministic, and that this makes free will impossible.
The principle of free will has religious, ethical, and scientific implications. For example, in the religious realm, free will may imply that an omnipotent divinity does not assert its power over individual will and choices. In ethics, it may imply that individuals can be held morally accountable for their actions. In the scientific realm, it may imply that the actions of the body, including the brain and the mind, are not wholly determined by physical causality. The question of free will has been a central issue since the beginning of philosophical thought.