or two others, but upon the immense background of our general knowledge
and beliefs, full of circumstances and analogies, in relation to which
alone any given proposition is intelligible. Indeed, for this reason, it
is impossible to illustrate Logic sufficiently: the reader who is in
earnest about the cogency of arguments and the limitation of proofs, and
is scrupulous as to the degrees of assent that they require, must
constantly look for illustrations in his own knowledge and experience
and rely at last upon his own sagacity.




CHAPTER III

OF TERMS AND THEIR DENOTATION


§ 1. In treating of Deductive Logic it is usual to recognise three
divisions of the subject: first, the doctrine of Terms, words, or other
signs used as subjects or predicates; secondly, the doctrine of
Propositions, analysed into terms related; and, thirdly, the doctrine of
the Syllogism in which propositions appear as the grounds of a
conclusion.

The terms employed are either letters of the alphabet, or the words of
common language, or the technicalities of science; and since the words
of common language are most in use, it is necessary to give some account
of common language as subserving the purposes of Logic. It has been
urged that we cannot think or reason at all without words, or some
substitute for them, such as the signs of algebra; but this is an