ain of causes and
effects unites each age with every other age that has gone before, is
one of the most memorable sentences in the history of thought. And
Turgot not only saw that there is a relation of cause and effect between
successive states of society; he had glimpses into some of the
conditions of that relation. To a generation that stands on loftier
heights his attempts seem rudimentary and strangely simple, but it was
these attempts which cut the steps for our ascent. How is it, he asked,
for instance, that the succession of social states is not uniform? that
they follow with unequal step along the track marked out for them? He
found the answer in the inequality of natural advantages, and he was
able to discern the necessity of including in these advantages the
presence, apparently accidental, in some communities and not in others
of men of especial genius or capacity in some important direction.[52]
Again, he saw that just as in one way natural advantages accelerate the
progress of a society, in another natural obstacles also accelerate it,
by stimulating men to the efforts necessary to overcome them: _le besoin
perfectionne l'instrument_.[53] The importance of following the march of
the human mind over all the grooves along which it travels to further
knowledge, was fully present to him, and he dwells repeatedly on the
constant play going on between discoveries in one science and those in
another. In no writer is there a fuller and more distinct sense of the
essential unity and integrity of the history of mankind, nor of the
multitude of the mansions into which this vast house is divided, and the
many keys which he must possess that would open and enter in.

Even in empirical explanations Turgot shows a breadth and accuracy of
vision truly surprising, considering his own youth and what we may
venture to call the youth of his subject. The reader will be able to
appreciate this, and to discern at the same time the arbitrary nature of
Montesquieu's method, if he will contrast, for example, the remarks of
this writer upon polygamy with the far wider and more sagacious
explanation of the circumstances of such an institution given by
Turgot.[54] Unfortunately, he has left us only short and fragmentary
pieces, but they suggest more than many large and complete works. That
they had a very powerful and direct influence upon Condorcet there is no
doubt, as well from the similarity of general conception between him and
T