hese, as the most typical man of his
time--Descartes. It is the Cartesian doubt--the maxim that assent may
properly be given to no propositions but such as are perfectly
clear and distinct--which, becoming incarnate, so to speak, in the
Englishmen, Anthony Collins, Toland, Tindal, Woolston, and in the
wonderful Frenchman, Pierre Bayle, reached its final term in Hume.

And, on the other hand, although the theory of Gravitation set
aside the Cartesian vortices--yet the spirit of the "Principes de
Philosophie" attained its apotheosis when Newton demonstrated all the
host of heaven to be but the elements of a vast mechanism, regulated
by the same laws as those which govern the falling of a stone to the
ground. There is a passage in the preface to the first edition of the
"Principia" which shows that Newton was penetrated, as completely
as Descartes, with the belief that all the phenomena of nature are
expressible in terms of matter and motion.

"Would that the rest of the phenomena of nature could be deduced by
a like kind of reasoning from mechanical principles. For many
circumstances lead me to suspect that all these phenomena may depend
upon certain forces, in virtue of which the particles of bodies, by
causes not yet known, are either mutually impelled against one another
and cohere into regular figures, or repel and recede from one another;
which forces being unknown, philosophers have as yet explored nature
in vain. But I hope that, either by this method of philosophizing, or
by some other and better, the principles here laid down may throw some
light upon the matter."[1]

[Footnote 1: "Utinam caetera naturae phaenomena ex principiis
mechanicis, eodem argumentandi genere, derivare licet. Nam multa me
movent, ut nonnihil suspicer ca omnia ex viribus quibusdam pendere
posse, quibus corporum particulae, per causas nondum cognitas, vel in
se mutuo impelluntur et secundum figuras regulares cohaerent vel ab
invicem fugantur et reced ent: quibus viribus ignotis, Philosophi
hactenus Naturam frustra tentarunt. Spero autem quod vel huic
philosophandi modo, vel veriori, alicui, principia hic posita lucem
aliquam praebebunt."--Preface to First Edition of _Principia_, May 8,
1686.]

But the doctrine that all the phenomena of nature are resolvable into
mechanism is what people have agreed to call "materialism;" and when
Locke and Collins maintained that matter may possibly be able
to think, and Newton himself could compare inf