l
Dogs, from which other sexless Dogs must proceed. At the end of a
certain number of terms of the series, the Dogs would acquire sexes and
generate young; but these young would be, not Dogs, but Hyaenas. In fact,
we have _demonstrated_, in Agamogenetic phaenomena, that inevitable
recurrence to the original type, which is _asserted_ to be true of
variations in general, by Mr. Darwin's opponents; and which, if the
assertion could be changed into a demonstration, would, in fact, be
fatal to his hypothesis.

XIV.

ON DESCARTES' "DISCOURSE TOUCHING THE METHOD OF USING ONE'S REASON
RIGHTLY AND OF SEEKING SCIENTIFIC TRUTH."

It has been well said that "all the thoughts of men, from the beginning
of the world until now, are linked together into one great chain;" but
the conception of the intellectual filiation of mankind which is
expressed in these words may, perhaps, be more fitly shadowed forth by a
different metaphor. The thoughts of men seem rather to be comparable to
the leaves, flowers, and fruit upon the innumerable branches of a few
great stems, fed by commingled and hidden roots. These stems bear the
names of the half-a-dozen men, endowed with intellects of heroic force
and clearness, to whom we are led, at whatever point of the world of
thought the attempt to trace its history commences; just as certainly as
the following up the small twigs of a tree to the branchlets which bear
them, and tracing the branchlets to their supporting branches, brings
us, sooner or later, to the bole.

It seems to me that the thinker who, more than any other, stands in the
relation of such a stem towards the philosophy and the science of the
modern world is Rene Descartes. I mean, that if you lay hold of any
characteristic product of modern ways of thinking, either in the region
of philosophy, or in that of science, you find the spirit of that
thought, if not its form, to have been present in the mind of the great
Frenchman.

There are some men who are counted great because they represent the
actuality of their own age, and mirror it as it is. Such an one was
Voltaire, of whom it was epigrammatically said, "he expressed
everybody's thoughts better than anybody."[68] But there are other men
who attain greatness because they embody the potentiality of their own
day, and magically reflect the future. They express the thoughts which
will be everybody's two or three centuries after them. Such an one was
Descartes.

Born, in 1