Actus primus
Actus primus, or first actuality, is a technical expression used in scholastic philosophy.[1] The Latin word actus means determination or complement.The complete substance constituted by these two principles receives further determinations, which are, in that respect, second actualities.Thus the extensive quantity of a substance is a first actuality when compared to the shape.The modern distinction of potential and kinetic energy might serve as another illustration: the loaded gun, or the engine with steam buildup, represent first actualities; the bullet speeding to the mark, the engine flying over the rails, represent second actualities.