Contexts -- Science -- Biology -- Mechanism
Two questions related to biological mechanism -- the degree to
which the behavior of organisms is determined by their
environment, and the reality of anything spiritual, as opposed to
material -- were widely debated by eighteenth-century scientists.
The opposition of a material body and an immaterial soul is very
ancient, and received biblical sanction in the Christian era. But
in the seventeenth and eighteenth centuries, many thinkers agreed
that biology plays a considerable part in influencing behavior;
Descartes, for instance, admits in the Discourse on
Method:
The mind is so intimately dependent upon the condition and
relation of the organs of the body, that if any means can ever be
found to render men wiser and more ingenious than hitherto, I
believe that it is in medicine they must be sought for.
The work of Locke, Condillac, and Hartley argued that the mind is
a tabula rasa, a blank slate, on which the environment
leaves impressions through the senses. Perception and even cognition
are treated not as acts requiring volition, but as the inevitable
consequence of the impression of stimuli on the senses. La Mettrie gives the most forcible
expression of this theory in L'homme machine (1748):
As a violin string or a harpsichord key vibrates and gives forth sound, so
the cerebral fibers, struck by waves of sound, are stimulated to render or
repeat the words that strike them. And as the structure of the brain is
such that when eyes well formed for seeing, have once perceived the image
of objects, the brain can not help seeing their images and their
differences, so when the signs of these differences have been traced or
imprinted in the brain, the soul necessarily examines their relations.
Others took these modest generalizations further, arguing against the
notion of a transcendent human nature, and advocating instead a model
whereby the characters of humans are dependent entirely on the stimulti to
which they are exposed. Montesquieu argued for the importance of
environmental determination; he pointed to the strong but barbaric
inhabitants of northern climates, compared to the refined and intellectual
but delicate southerners. Scientists such as Boerhaave and (most
famously) La Mettrie provided a scientific basis to the theory. La
Mettrie's conclusion to L'homme machine notable for its directness:
Let us then conclude boldly that man is a machine, and that in the whole
universe there is but a single substance differently modified.
Although Linnaeus resisted strict
mechanical explanations of behavior early in his career, he gave
increasing credence to the belief, as reflected in his revisions to the
twelve editions of the Systema naturae that appeared in his
lifetime. Lamarck, however, while
granting that the behavior of the most primitive species is determined by
their environment, believed that more advanced species grew increasingly
self-determined.
Mechanism had implications beyond the sciences, and could be extended from
simple biology to other human endeavors. La Mettrie, for instance, applies
the model to education in L'homme
machine:
Nothing, as any one can see, is so simple as the mechanism of our
education. Everything may be reduced to sounds or words that pass from the
mouth of one through the ears of another into his brain. At the same
moment, he perceives through his eyes the shape of the bodies of which
these words are the arbitrary signs.
