reasons (e.g. achievement, affiliation and power) that drive, direct and select an individual's behaviour.

The reason why someone commits a crime.

a reason for doing something

A factor that determines a person's choice of one course of behaviour from among several possibilities.

In law, especially criminal law, a motive is the cause that moves people and induce a certain action. Motive in itself is seldom an element of any given crime; however, the legal system typically allows motive to be proven in order to make plausible the accused's reasons for committing a crime, at least when those motives may be obscure or hard to identify with.