Original: Additionally, things can be causes of one another, reciprocally causing each other, as hard work causes fitness, and vice versa - although not in the same way or by means of the same function: the one is as the beginning of change, the other is as its goal.
Simplified: This includes modern ideas of causation, such as wanting or needing something to be, or those that give a purpose to behaviour Additionally, things can be causes of one another as hard work causes fitness, and vice versa.