necessity for clearness and certainty in physics and
metaphysics as in mathematics, and of his consequent
demand that all complex conceptions be capable of
analysis into elements that are transparent to the
mind. There was only one other thinker in his day
inspired by such an intellectual ideal, and that was
Galileo, who by his pursuit of it in the physical
sphere created the science of mechanics. If, says
Descartes, ¹ magnetism is a qualitatively distinct
force, and not merely the resultant of a complex of
mechanical conditions, we are forever debarred from
knowing it; ² and we are debarred from knowing
all that which is not explicable in terms of the few
ultimate conceptions with which consciousness is
endowed. What these ultimate conceptions are, and
how far they render knowledge possible, it is the
work of his metaphysics to show.

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