4. Thirdly, Σημειωτική.
Thirdly, the third branch may be called Σημειωτικὴ, or the doctrine of signs; the most usual
whereof being words, it is aptly enough termed also Λογικὴ, logic: the business whereof is to consider the nature
of signs, the mind makes use of for the understanding of things, or conveying its knowledge to others. For, since
the things the mind contemplates are none of them, besides itself, present to the understanding, it is necessary that
something else, as a sign or representation of the thing it considers, should be present to it: and these are ideas.
And because the scene of ideas that makes one man's thoughts cannot be laid open to the immediate view of
another, nor laid up anywhere but in the memory, a no very sure repository: therefore to communicate our
thoughts to one another, as well as record them for our own use, signs of our ideas are also necessary: those which
men have found most convenient, and therefore generally make use of, are articulate sounds. The consideration,
then, of ideas and words as the great instruments of knowledge, makes no despicable part of their contemplation
who would take a view of human knowledge in the whole extent of it. And perhaps if they were distinctly
weighed, and duly considered, they would afford us another sort of logic and critic, than what we have been
hitherto acquainted with.
