Abednego recorded some of his observations of the design language of scientists at a conference he was at. I wanted to connect this with some of the stuff I've been looking into among the ancient and medieval philosophers I've been reading a lot of lately. These scientists are basically doing what Aristotle did. He would speak of trees as having roots in order that they can derive nutrients from the soil, which is for the purpose of growing tall. Most of the materialist philosophers of that time, particularly a number of pre-Socratics, the Hippocratic school, and the Epicureans, said this didn't make any sense, because you can tell an entirely material story about how one thing causes another and leads things to happen, without mentioning purposes at all.
Aristotle wanted to say that this is just ignoring the different kinds of explanations for things. There are efficient causes, which those materialists were talking about, and then there are the final causes, which are goals or aims built into nature. This isn't supposed to be what we nowadays call a cause but simply a purpose that things, by their very nature, tend toward. Some of the neo-Platonists made the point that you could have divine causes and materialist causes, just talking about different levels of explanation.
What happens with Aquinas is very interesting. Before his time there wasn't much interaction with Aristotle, because his texts had been lost. Aquinas thoroughly absorbed Aristotle's works once they were translated into Latin, and he accepted the Aristotelian picture on this issue, with one modification. He didn't think Aristotle had a right to be talking about these purposes in nature unless a mind had given those purposes. He still saw them as final causes, not efficient causes, and thus they would be the sort of thing that modern science isn't supposed to talk about. Yet modern scientists do talk about it all the time. It's just that they have no right to, Aquinas would say, unless they're also willing to talk about an intelligent designer. Aristotle didn't want to call it design, but his view amounts to pretty much the same thing as what contemporary scientists call design when they don't want to speak of a designer. The question is whether they can get away with it if they don't believe in a designer.
Update: Mark Olson sees the main issue here as Why vs. What questions. That's not quite the idea. It's Why vs. How. Efficient causes explain how something comes about. Empedocles makes fun of those who offer divine explanations by pointing out that a bull born with one horn isn't caused in some miraculous way by a god but can be explained through normal mechanisms of nature. That's how it came about. Plutarch the neo-Platonist steps in to say that that's just the how. The why might well be a divine explanation for why those efficient causes were arranged in the way they were in order to produce a creature born as an omen. Final causes answer why, and efficient causes answer how.