Video from The Thomistic Institute
"Is there such a thing as human nature, or is that simply a conventional idea? Think about an adolescent; that adolescent used to be a baby; that baby used to be an embryo. Then, you look at that same human being ten years later and it is an adult… and then later it is an even older person. Yet, there is something that remains through all that. It is more than just the name; that remaining thing is the nature, the natural kind as a principle of continuity and development. Aristotle describes nature as a principle or cause of motion and rest in that to which it [the nature] belongs primarily and per se. Nature and Natures (Aquinas 101) - Fr. Thomas Joseph White, O.P." from video introduction.