Man always acts for an end, irrational creatures never
Man acts for known end. But there are many things that have no knowledge of an end; either because they are altogether without knowledge, as insensible creatures: or because they do not apprehend the idea of an end as such, as irrational animals.
Objection 1. It would seem that it is proper to the rational nature to act for an end. For man, to whom it belongs to act for an end, never acts for an unknown end. On the other hand, there are many things that have no knowledge of an end; either because they are altogether without knowledge, as insensible creatures: or because they do not apprehend the idea of an end as such, as irrational animals. Therefore it seems proper to the rational nature to act for an end.