Substance perceived under the Attribute of Extension. Again,
we know a world of thoughts, feelings, mental events, or however
we may call its elements, to which the notions of space and
extension are wholly inapplicable ; we cannot ascribe mass to a
sensation, or resolve a thought into atoms. And this is the
domain of Substance perceived under the Attribute of Thought.
It is to be observed that, inasmuch as Attribute is defined by
reference to intellect, and Thought is itself an attribute. Thought
appears to be in a manner counted twice over. Likewise Ex-
tension and Thought, although they are the only Attributes we
have anything to do with, are in Spinoza's view only two out of
an infinite number. But the difficulties that arise on both these
points are better postponed for a while.
