BOOK I PART IV
each other. At the same time it assigns to each
of these species of objects a distinct substan-
tial form, which it supposes to be the source of
all those different qualities they possess, and to
be a new foundation of simplicity and identity
to each particular species. All depends on our
manner of viewing the objects. When we look
along the insensible changes of bodies, we sup-
pose all of them to be of the same substance or
essence. When we consider their sensible dif-
ferences, we attribute to each of them a sub-
stantial and essential difference. And in or-
der to indulge ourselves in both these ways of
considering our objects, we suppose all bodies
to have at once a substance and a substantial
form.
The notion of accidents is an unavoidable
consequence of this method of thinking with