The standard design-theorist argument hinges on the assumption that there are three logically distinct kinds of explanation: chance, necessity, and design. (I say “explanation” rather than “cause” in order to avoid certain kinds of ambiguities we’ve seen worked out here in the past two weeks).
This basic idea — that there are these three logically distinct kinds of explanation — was first worked on by Plato, and from Plato it was transmitted to the Stoics (one can see the Stoics use this argument in their criticism of the Epicureans) and then it gets re-activated in the 18th-centuries following, such as in the Christian Stoicism of the Scottish and English Enlightenment, of which William Paley is a late representative. Henceforth I’ll call this distinction “the Platonic Trichotomy”
There are at least two different ways of criticizing the Platonic Trichotomy. One approach, much-favored by ultra-Darwinists, is to argue that unplanned heritable variation (“chance”) and natural selection (“necessity,” if natural selection is a “law” in the first place) together can produce the appearance of design. (Jacques Monod is a proponent of this view, and perhaps Dawkins is today.) The other approach, which I prefer, is to reject the entire Trichotomy.
To reject the Trichotomy is not to reject the idea that speciation is largely explained in terms of the feedback between variation and selection, but rather to reject the idea that this process is best conceptualized in terms of “chance” and “necessity.”
So what’s the alternative? What we would need here is a new concept of nature that is not beholden to any of the positions made possible with respect to the conceptual straitjacket imposed by the Trichotomy.
, and the evidence of complex life as 
. What we want to know is the posterior probability that 
is true, given ![\[P(H_{G}|L_N)}\]](http://theskepticalzone.com/wp/wp-content/ql-cache/quicklatex.com-3f2ddf730ccbd821f6f5020f49419cdb_l3.png "Rendered by QuickLaTeX.com")
