we say "they exist," "they are known," or the like, these words must not
be thought to signify anything common to both natures. There is nothing
alike or common in them: and to expect that by any multiplication or
enlargement of our faculties we may be enabled to know a spirit as we do
a triangle, seems as absurd as if we should hope to see a sound. This is
inculcated because I imagine it may be of moment towards clearing several
important questions, and preventing some very dangerous errors concerning
the nature of the soul. We may not, I think, strictly be said to have an
idea of an active being, or of an action, although we may be said to have
a notion of them. I have some knowledge or notion of my mind, and its
acts about ideas, inasmuch as I know or understand what is meant by these
words. What I know, that I have some notion of. I will not say that the
terms idea and notion may not be used convertibly, if the world will have
it so; but yet it conduceth to clearness and propriety that we
distinguish things very different by different names. It is also to be
remarked that, all relations including an act of the mind, we cannot so
properly be said to have an idea, but rather a notion of the relations
and habitudes between things. But if, in the modern way, the word idea is
extended to spirits, and relations, and acts, this is, after all, an
affair of verbal concern.

143. It will not be amiss to add, that the doctrine of abstract ideas has
had no small share in rendering those sciences intricate and obscure
which are particularly conversant about spiritual things. Men have
imagined they could frame abstract notions of the powers and acts of the
mind, and consider them prescinded as well from the mind or spirit
itself, as from their respective objects and effects. Hence a great
number of dark and ambiguous terms, presumed to stand for abstract
notions, have been introduced into metaphysics and morality, and from
these have grown infinite distractions and disputes amongst the learned.