4. Potentiality and actuality
1. Being in motion
Heraclitus said that we do not bathe twice at the same river because water is different. According to this Greek philosopher you cannot say that something is, but is and is not. It is a thing and is stop being that thing to be another one, because it is changing, transforming.
According to Parmenides being is and not being is not. It is impossible to be transition from being to not being and so there is no motion. Motion is apparent. In fact, being is unchangeable.
Facing these opposite positions, Aristotle found out the right solution. He accepts that there is being and motion.
There are two principles in being: potentiality and actuality. In every being there is something potential and something actual. The actual being: what really is, what already is. The potential being: what is not yet, but can be.
We must not deny being nor motion. What exists in fact is being in motion, stay and change.