Thursday, April 20, 2006


Sagan's Implicit Endorsement of Specified Complexity as a Design Detector

In The Demon Haunted World Carl Sagan debunks a number of claims about purported instances of design. For example:

'There was a celebrated eggplant that closely resembled Richard M. Nixon. What shall we deduce from this fact? Divine or extraterrestrial intervention? Republican meddling in eggplant genetics? No. We recognize that there are large numbers of eggplants in the world and that, given enough of them, sooner or later we'll come upon one that looks like a human face, even a very particular human face.' (p. 47.)

Notice that the suggestion of design here is based upon the fact that the eggplant in question exhibits a specification - an independently given pattern. In this case, the specification is looking like a human face, and more than that, looking like a particular human face (Nixon - although it is hard to believe that the resemblance can have been all that tight). That the eggplant exhibits this specification is implicitly accepted by Sagan. So why does Sagan reject the idea that the correspondence between the eggplant and the Nixon specification is the result of design? Because the example lacks complexity. Given the number of human faces and eggplants that have existed Sagan argues that it is not all that unlikely that we'd come accross an eggplant that bore a resemblance to a human face, even to Nixons. Hence we don't have to deduce divine, or extraterrestrial, or Republican design from the eggplant. Note that Sagan's argument for rejecting a design inference from the eggplant implicitly accepts that if the eggplant exhibited a specification at a sufficient level of complexity then a design inference would be justified. In other words, Sagan recognized that a design inference is warranted when faced with an example of 'complex specified information' or 'specified complexity'. This is why, in order to debunk a proposed instance of design which he admits exhibits specification, Sagan argues that the proposed example lacks sufficient complexity.

Note also that Sagan implicitly endorses the point made by many ID theorists that while specified complexity warrants an inference to 'intelligent design', it does not in and of itself warrant an inference to any particular designer: 'Divine or extraterrestrial intervention? Republican meddling in eggplant genetics?' All three explanations would be possible candidates if a design inference in this case were justified.

Sagan goes on to discuss the infamous so-called 'face on Mars', first photographed by one of the Viking orbiters in 1976. Sagan argues against a design inference in this instance as well. How does he do it? By arguing that the 'face' is neither very complex nor tightly specified. First he examines the complexity of the 'face':

'Mars has a surface area of almost 150 million square kilometers. Is it so astonishing that one (comparatively) postage-stamp-sized patch in 150 million should look artificial - especially given our penchant, since infancy, for finding faces?' (p. 56.)

In other words, it is not all that unlikely that a small area of Mars should look sufficiently like a face to make it appear face-like to casual observation. Then he goes after specification:

'If we study the original image more carefully, we find that a strategically placed 'nostril' - one that adds much to the impression of a face - is in fact a black dot corresponding to lost data in the radio transmission from Mars to Earth. The best picture of the Face shows one side lit by the Sun, the other in deep shadow. Using the original digital data, we can severely enhance the contrast in the shadows. When we do, we find something rather unfacelike there. The Face is at best half a face... the Martian sphinx looks natural - not artificial, not a dead ringer for a human face.' (p. 56, my italics.)

In other words, while at first glance the 'face' seems to exhibit a specification, a closer look shows that it doesn't. In Richard Dawkin's terminology, the supposed face on Mars is 'designoid'; it gives a superficial impression of design at first glance, but the more we investigate its salient features, the less designed it looks. Hence Sagan concludes: 'It was probably sculpted by slow geological processes over millions of years.' (p. 56)

The important point here is that in order to justify this conclusion Sagan seeks to undermine precisely those twin features of things that design theorists recognize as jointly sufficient conditions for justifying a design inference: namely complexity and specification.

If Sagan is right to argue that the 'face' is not designed because it fails to exhibit specified complexity (indeed, because it is neither sufficiently complex nor tightly specified) then design theorists must be right to argue that anything which does exhibit specified complexity should be attributed to intelligent design.

For example, Sagan wouldn't argue that the presidential faces on Mount Rushmore were 'sculpted by slow geological processes', because unlike the Nixon eggplant and the 'face' on Mars, Mount Rushmore does exhibit specified complexity.

Although he doesn't use the terminology of 'specified complexity' Sagan implicitly endorses specified complexity as an adequate criterion of intelligent design, arguing that design inferences cannot be supported when the putative designed object lacks complexity or speficiation or both. This negative argument implies the positive argument that when a putative designed object exhibits specified complexity then a design inference is warranted.

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