What does Aquinas mean by “act for an end?”

Consider goal-directed systems. Think of guided missles and blenders and watches and all manner of things that have apparent purpose in their functions. They all act for different ends, but they are all goal-directed.

Now consider that human beings act toward ends because they have desires connected with ends, purposes, and goals.

• Human beings are capable of goal-directed behavior because they have minds.

• Guided missiles are goal-directed systems, but they don’t have minds.

• Recall the second premise in Aquinas' argument that we considered on the last step (A being that acts for an end, but does not itself have a mind, must have been designed by a being that has a mind.) So, for example, guided missiles are artifacts—built by beings with minds.
  >>> Inferences

• Non-human organisms like plants and bacteria—that don’t apparently have beliefs and desires—seek out nutrients and avoid toxic substances: survival and reproduction goals.

• For Aristotle and Aquinas, even inanimate beings/objects have goals or ends toward which they strive.