What actually is "design"

I've been wondering of late what it is that is explained when something is called "designed". The older design theorists had no such trouble - Aquinas, for example, noted that

... things which lack intelligence, such as natural bodies, act for an end, and this is evident from their acting always, or nearly always, in the same way, so as to obtain the best result. Hence it is plain that not fortuitously, but designedly, do they achieve their end. [Summa, 1Q2.iii]

This is a wonder of spare and elegant prose, as always with Aquinas. Modern readers may miss the "has an end" and the meaning of "fortuitously". Something has an end if it is for that reason it does whatever it does. And something is fortuitous if it does not happen by necessity. These are old, Aristotelian, categories of metaphysics. It is my opinion that they were developed by Aristotle and his successors as an attempt at science, not grand philosophy. You can explain things with an end/efficient/material/formal cause distinction. And so Aristotle and crew explained their world by positing that they had natures which included an end, and which had necessary properties referred to as "essences", and "accidental" properties which were fortuitous and unnecessary.

Anyway, much of the ... err... necessity for these categoricals is gone from science. We can have things develop from egg to adult without "ends". In effect we explain this mostly in what Aristotle would call "material" (the properties of the matter from which things are made) and "efficient" (the actual motive forces) causes. Ends are not required in the paradigmatic cases of living things.

Aquinas continued, presenting the locus classicus of the Argument from Design:

Now, whatever lacks intelligence cannot move towards an end, unless it be directed by some being endowed with knowledge and intelligence; as the arrow is shot to its mark by the archer. Therefore some intelligent being exists by whom all natural things are directed to their end; and this being we call God.

Once we lose the need for an ends-metaphysics, a teleology or entelechy (that is, a general external view of ends being imposed, or a specific view of ends being innate, respectively), we lose the force of this argument, but it is a pretty good attempt at the time to explain all the physical and in particular biological phenomena we see around us. [Incidentally, Aristotle restricted ends to living things; his successors were not so spare.]

But we no longer need it. We no longer need it in the matter of development, which is explained now as the outworking of the physical properties of the constituent elements of living organisms in a given environment (internal and external always need to be included here - chicken eggs don't develop well in space). And we no longer need it in the matter of how organisms came to be as they are - natural selection and the rest of evolutionary theory obviates that. So Aquinas quick and easy conclusion carries no formal force to us - there is an alternative.

But the modern intelligent design-theorists, the IDevotees, as I have called them, are not arguing to the existence of a designer, a point noted by that somewhat notorious philosopher Anthony Flew in his book Darwinism. Now they are arguing from a designer to an explanation of the properties of living things. Somehow, "design" is an explanation of why bacteria have flagella, why we have hemoglobin, and so on. So what is "design" that it explains anything?

This is something I'll follow up next time. Cheers