The determinist, then, assumes that everything that occurs is a function of a finite number of causes and that, if these causes were known, an event could be predicted with complete accuracy. However, knowing all causes of an event is not necessary; the determinist simply assumes that they exist and that as more causes are known, predictions become more accurate.

The assumption that what is being studied can be understood in terms of causal laws is called determinism. Richard Taylor defined determinism as the philosophical doctrine that “states that for everything that ever happens there are conditions such that, given them, nothing else could happen.”

For example, almost everyone would agree that the weather is a function of a finite number of variables such as sunspots, high-altitude jet streams, and barometric pressure; yet weather forecasts are always probabilistic because many of these variables change constantly, and others are simply unknown.