BOOK I PART IV
thing else, which we can imagine: and there-
fore it is impossible to conceive, how they can
be the action or abstract mode of any substance.
The instance of motion, which is commonly
made use of to shew after what manner percep-
tion depends, as an action, upon its substance,
rather confounds than instructs us. Motion to
all appearance induces no real nor essential
change on the body, but only varies its rela-
tion to other objects. But betwixt a person in
the morning walking a garden with company,
agreeable to him; and a person in the afternoon
inclosed in a dungeon, and full of terror, de-
spair, and resentment, there seems to be a rad-
ical difference, and of quite another kind, than
what is produced on a body by the change of
its situation. As we conclude from the distinc-
tion and separability of their ideas, that exter-
nal objects have a separate existence from each