ct, it may be claimed for his view. He thinks with Berkeley that
objects of sight are quite distinct from those of touch, and that the
one therefore cannot give any assurance of the other; and he asks the
Cartesians to consider how far God's truth and goodness are called in
question by their denial of the externality of the secondary
qualities. The second part of the book is taken up with a number of
metaphysical arguments to prove the impossibility of an external
world. The pivot of this part is the logical principle of
contradiction. From the hypothesis of an external world a series of
contradictions are deduced, such as that the world is both finite and
infinite, is movable and immovable, &c.; and finally, Aristotle and
various other philosophers are quoted, to show that the external
matter they dealt with, as mere potentiality, is just nothing at all.
Among other uses and consequences of his treatise, Collier thinks it
furnishes an easy refutation of the Romish doctrine of
transubstantiation. If there is no external world, the distinction
between substance and accidents vanishes, and these become the sole
essence of material objects, so that there is no room for any change
whilst they remain as before. Sir William Hamilton thinks that the
logically necessary advance from the old theory of representative
perception to idealism was stayed by anxiety to save this miracle of
the church; and he gives Collier credit for being the first to make
the discovery.

His _Clavis Universalis_ is interesting on account of the resemblance
between its views and those of Berkeley. Both were moved by their
dissatisfaction with the theory of representative perception. Both
have the feeling that it is inconsistent with the common sense of
mankind, which will insist that the very object perceived is the sole
reality. They equally affirm that the so-called representative image
is the sole reality, and discard as unthinkable the unperceiving
material cause of the philosophers. Of objects of sense, they say,
their _esse_ is _percipi_. But Collier never got beyond a bald
assertion of the fact, while Berkeley addressed himself to an
explanation of it. The thought of a distinction between direct and
indirect perception never dawned upon Collier. To the question how all
matter exists in dependence on percipient mind his only reply is,
"Just how my reader pleases, provided it