226 J.J. Haldane
it is here that the problem arises. For Smart’s comments on Behe, see
pp. 213 –14.
The development of species depends upon an array of complex activit-
ies occurring within organisms at the biochemical level. These comprise the
‘black box’ of whose contents Darwin had no idea. Complexity as such is
to be expected, but that which Behe has in view is not simply a matter of
intricacy and detail. Rather, as in the case of the origins of cellular organisms,
it is that of interdependent functionality between parts. Behe’s favoured
example is the bacterial flagellum. This is an element located in the mem-
brane of a cell which acts as a rotary propeller. The ‘motor’ is located at
the base of the flagellum and is itself composed of several parts. Like many
other biological systems this has the feature that in the absence of any one of
its components and of their relevant interaction, it would not function.
One cannot say, therefore, that the system itself evolved piece by piece, and
it would not be credible to suppose that in this and the other cases of irre-
ducible complexity the systems resulted from accidental contemporaneous
assemblages of their interdependent elements. The systems only work if all
parts are present, correct and functioning cooperatively. Recalling Paley’s
example of the watch, Behe offers as an analogy the construction and opera-
tion of a traditional mouse trap. If any of the components is missing or
broken, the trap fails to function; and one cannot envisage a more primitive
‘proto-mousetrap’ operating without a spring, say. The system only exists
when all its parts are in place and are performing in accord with the overall
functional structure.
Like the case of reproduction (see chapter 2, section 4, above) irreducible
complexity does not admit of degrees and therefore it cannot be represented
as emerging by stages. Either an entity exhibits it or it does not, and the
transition from one condition to the other is not naturalistically explicable.
Of course, if it were an artefact then it would be accountable for by reference
to design. Frederick Hoyle and Francis Crick have speculated about extra-
terrestrial agents sowing seeds of life, but as was said earlier this hypothesis
is regressive (to say nothing of its implausibility). So we face an eliminative
induction. There are, I suggest, only three broad possibilities. Naturalism
maintains that functional animate complexity has evolved by natural means
from non-functional, inanimate matter. Panvitalismwould have it that irre-
ducibly complex organic life of some sort has always existed and that it has no
natural explanation, which is to say it either has no explanation at all, or that
its explanation is design. Creationismmaintains that irreducible complexity
and other aspects of natural teleology are due to design (whether they have
always existed is a separate matter). Naturalism, I have argued, must fail for
want of being able to account for radical emergence. Panvitalism is either
silent on the issue of explanation or defers to Creationism. Thus, the hypothesis