Annals of the History and Philosophy of Biology

86
Annals of the History and Philosophy of Biology, Vol. 10 (2005)
Peter McLaughlin
Thus, Buffon’s table gives his best estimate of the dates at which the surface temperatures
of the various celestial bodies dropped down to a temperature where life is possible.
Let us accept Buffon’s estimates of the dates at which the physical conditions of life
become available on various planets. But we still need some further assumptions before
we can deduce the existence of life from its mere physical possibility.
Assumption 2: Reductionism or mechanistic determinism: all bodies or systems are unequivocally
determined by the intrinsic properties of their parts and by the laws governing
the motions and interactions of the parts.
Plausible implications
1) Under the same conditions the same kinds of particles will or will tend to
combine into and determine the same kinds of material systems.
2) Buffon concludes: as soon as the temperature drops a certain amount below
the boiling point of water organic molecules arise. Once organic molecules have
arisen they begin to combine due to mechanical and chemical forces. All possible
combinations are attempted; all stable combinations become fixed. Some of
these are not only stable but also viable: these are organisms. All species of organisms
that are viable and reproducible under these physical conditions must
exist. Each of the planets has in principle the same spectrum of animals and
plants as does the Earth.
As Buffon puts it: Given the same matter, “the same temperature supports, produces
everywhere the same beings” (Buffon 1775, 510). 3
We can check the correctness of this interpretation of the constraints on theory formation
by a thought experiment. What would happen if some catastrophe occurred and
wiped out all the inhabitants of a planet but afterwards allowed the physical conditions to
return to normal? Buffon seems to be committed to the proposition that all the species
wiped out in the conflagration would return again very soon. And in fact he plays
through this experiment and accepts exactly this conclusion, merely assuming the organisms
would be somewhat smaller due to the cooling of the earth and that the larger species
might not make it the second time around (1777, 363–367). This very same thought
experiment was carried out explicitly by Blumenbach with the same results: the same
vital force working on the same materials would produce the same spectrum of organic
forms. Moreover, Blumenbach even takes such a catastrophe or “total revolution” actually
to have occurred in a preadamite period.
On the whole the creator surely let the same forces of nature act to bring about the new organic
realms as fulfilled this intention in the previous world. Except that in the production of the new
species the formative drive (Bildungstrieb) had to take a direction more or less deviating from the
previous one due to matter’s being differently modified by such a total revolution. (1806, 19–20)
3 Buffon does not take up the question of whether the same species on different planets might look somewhat
different given that the gravitational fields are significantly different.