Determinism is the idea that everything that happens, including all human actions, is completely determined by prior events. There is only one possible future, and it is completely predictable in principle, most famously by Laplace’s Supreme Intelligent Demon, assuming perfect knowledge of the positions and velocities of all the atoms in the void.
More strictly, determinism should be distinguished from pre-determinism, the idea that the entire past (as well as the future) was determined at the origin of the universe, and from pre-destination, the idea that the will of an omniscient supreme being has determined the one possible future.
Determinism is sometimes confused with causality, the idea that all events have causes. But some events may be undetermined by prior events. Such an event is indeterminate, sometimes known as a “causa sui” or self-caused event. But it may in turn be the cause for following events that would therefore not be predictable from conditions before the uncaused event.
Although there is only one basic form of indeterminism, there are many determinisms, depending on what pre-conditions are considered to be determinative of an event or action. We identify more than a dozen distinguishable determinisms.