Matson presents the “Humean” design inference in the following manner:
(1) Natural objects share with artifacts the common characteristics of adjustment of parts and curious adapting of means to ends.
(2) Artifacts have these characteristics because they are products of design.
(3) Natural objects are probably products of a great designer. (84)
He has 2 objections to it. First, this argument is “by analogy” and resembles too well an utterly fallacious reasoning such as:
(4) Natural objects share with artifacts the common characteristic of being colored.
(5) Artifacts are colored by being painted or dyed.
(6) Natural objects are probably colored by a great painter-dyer. (85)
My reply is that if we inspect any object that exhibits specified complexity (SC) (for “curious adapting,” etc.) for which we can find out by other means whether it was intelligently designed, then it will turn out that it actually was intelligently designed. It will then stand to reason that even SC objects for which we have no other evidence that they were products of intelligent design still were products of intelligent design also.
Color, on the other hand, cannot spark a design inference. That X is red is no reliable indicator of X’s having been designed, because many red objects that are such that we know whether or not they were products of ID (by evidence other than their color), were not in fact products of ID. Unlike SC objects. As a result, (3) follows, and (6) does not.
Second, Matson suggests that we are often “able to tell whether something is an artifact without knowing what it is for or whether its parts are accurately adjusted.” (88) That’s very true. (Note that complexity, purpose, and design inference are 3 different things.) Sometimes design may be inferred through something other than specified complexity. This does not affect the point that SC is in itself a reliable indicator of design. SC is sufficient for a design inference, even if not necessary. But no more than this is needed for ascribing design to many “natural objects” such as biological systems.
If we restrict our attention to SC, then we may indeed miss a few instances of design, such as based on “machining, materials that do not exist in nature, regular markings, and the like.” (89) There may be false negatives. But there will not be false positives; SC is almost fully guaranteed to yield correct inferences. Once again (3) follows from (1) and (2), even if on occasion we might fail to detect design via those premises.