separate questions as possible;
that each part being more easily conceived, the whole may be more
intelligible--(Analysis).

3. To conduct the examination with order, beginning by that of objects
the most simple, and therefore the easiest to be known, and ascending
little by little up to knowledge of the most complex--(Synthesis).

4. To make such exact calculations and such circumspections as to be
confident that nothing essential has been omitted.

Consciousness, being the ground of all certainty, everything of which
you are clearly and distinctly conscious must be true; everything which
you clearly and distinctively conceive exists, if the idea of it
involves existence.

In the four rules, and in this view of consciousness, we have only half
of Descartes' system; the psychological half. It was owing to the
exclusive consideration of this half that Dugald Stewart was led--in
controverting Condorcet's assertion that Descartes had done more than
either Galileo or Bacon toward experimental philosophy--to say that
Condorcet would have been nearer the truth if he had pointed him out as
the "Father of the Experimental Philosophy of the Mind." Perhaps the
title is just; but Condorcet's praise, though exaggerated, was not
without good foundation.

There is, in truth, another half of Descartes' system, equally
important, or nearly so: we mean the deductive method. His eminence as a
mathematician is universally recognized. He was the first to make the
grand discovery of the application of algebra to geometry; and he made
this at the age of twenty-three. The discovery that geometrical curves
might be expressed by algebraical numbers, though highly important in
the history of mathematics, only interests us here by leading us to
trace his philosophical development. He was deeply engrossed in
mathematics; he saw that mathematics were capable of a still further
simplification and a far more extended application. Struck as he was
with the certitude of mathematical reasoning, he began applying the
principles of mathematical reasoning to the subject of metaphysics. His
great object was, amid the scepticism and anarchy of his contemporaries,
to found a system which should be solid and convincing. He first wished
to find a basis of certitude--a starting-point: this he found in
consciousness. He next wished to find a method of certitude: this he
found in mathematics.

"Those long chains of reasoning," he tells us, "all simple and