# Axiom of Causality

The Axiom of Causality is the proposition that everything in the universe has a cause and is thus an effect of that cause. This means that if a given event occurs, then this is the result of a previous, related event. If an object is in a certain state, then it is in that state as a result of another object interacting with it previously.

According to William Whewell the concept of causality depends on three axioms:[1]

1. Nothing takes place without a cause
2. The magnitude of an effect is proportional to the magnitude of its cause
3. To every action there is an equal and opposed reaction.

A similar idea is found in western philosophy for ages (sometimes called Principle of Universal Causation (PUC) or Law of Universal Causation), for example:

In addition, everything that becomes or changes must do so owing to some cause; for nothing can come to be without a cause. — Plato in Timaeus

Modern version of PUC is connected with Newtonian physics, but is also criticized for instance by David Hume.[2] Since then his view on the concept of causality is often predominating (see Causality, After the Middle Ages). Kant opposed Hume in many aspects, defending the objectivity of universal causation[3] (see: Causal thinking).

Example for the axiom: if a baseball is moving through the air, it must be moving this way because of a previous interaction with another object, such as being hit by a baseball bat.

An epistemological axiom is a self-evident truth. Thus the "Axiom of Causality" implicitly claims to be a universal rule that is so obvious that it does not need to be proved to be accepted. Even among epistemologists, the existence of such a rule is controversial. See the full article on Epistemology.

## Spontaneity

One implication of the Axiom is that if a phenomenon appears to occur without any observable external cause, the cause must be internal. See Compatibilism.

### Variation

Another implication of the Axiom is that all change in the universe is a result of the continual application of physical laws.

### Determinism

If all events are cause and effect relationships that follow universal rules, then all events—past, present and future—are theoretically determinate. See Causal determinism.

### First Cause

Main article: First Cause

If all effects are the result of previous causes, then the cause of a given effect must itself be the effect of a previous cause, which itself is the effect of a previous cause, and so on, forming an infinite logical chain of events that can have no beginning. See the cosmological argument.