St. Thomas borrows the principle “good is what all things desire” from Aristotle, and along with Aristotle he sees the “all things” as being said distributivity to include every single nature whatsoever. This absolute and distributive character of the good extending to all things arises from his understanding of natural science (notice that while Aristotle has a less dramatic presentation of the absolute causality of the good than Plato, he gives it a causality just as universal as Plato)
One of Aristotle’s most dramatic breaks with his predecessors was his insistence that there was a science of nature. This was an extremely controversial point in his day and it took a good deal of argument to establish. Parmenides- one of his main rivals- had a very extensive account of natural activities, and there would have been no contradiction if this account developed to the point of including all the things now known by natural science, but Parmenides considered this account of things to be mere opinion. This is why Aristotle deals with Parmenides at the very beginning of his account of natural science- he knows that the Parmenidean account of motion as not really existent needs to be dispelled first. (This idea of science as about “opinion” or “appearances” is familiar to us as Positivism.)
But what Aristotle recognized clearly, is that a science of nature requires nature to perform ordered processes as opposed to processes where absolutely anything can come forth from absolutely anything. “Good” enters the discussion as the name of the cause which is responsible for why this anything-from-anything state of affairs is not so. Notice that good arises as accounting for the difference between any sort of order and absolute disorder. Aristotle was aware that there was more than one kind of order: some kinds of order in nature could happen by necessity, others only for the most part, others rarely but still intentionally (the perfect novel, the arising of perfect members of the species) others involve sheer chance (like Church bingo night, coin-flips at the beginning of football games, mixing in flour, pollination, and seed-scattering), but a discussion of the kinds of ordered process is logically posterior to the question of whether there is some ordered process at all. Such processes are for goals, i.e. goods.
All this would be quite obvious, I think, if modern people were not bewitched by the gargoyle fear-totem of “blind forces”. This intrinsically absurd notion (forces can no more be blind than last Thursday can) is a false idol which in many ways is more insidious than Molech, since Molech only demanded the sacrifice of those goods which follow natural reproduction while the god “blind forces” demands that we sacrifice all the goods of nature absolutely. The speculative error in “blind forces” is that forces, as such, do not execute a directed process at all. Force only comes to have a direction when it is used as the tool of something with soul, as Sean Collins shows here (and which Plato showed long ago in the tenth book of the Laws)