[1] I am indebted to an unpublished manuscript of Mr. S. Klyce of Winchester, Massachusetts, for the significance of the fact that our words divide into _terms_ (of which more in the sequel) and into names which are not (strictly speaking) terms at all, but which serve to remind us of the vast and vague continuum, select portions of which only are designated by words as _terms_. He calls such words "infinity and zero" words. The word "experience" is a typical instance of an "infinity word." Mr. Klyce has brought out very clearly that a direct situation of experience ("situation" as I employ it is another such word) has no need of any word for itself, the thing to which the word would point being so egregiously there on its own behalf. But when communication about it takes place (as it does, not only in converse with others, but when a man attempts a mutual reference of different periods of his own life) a word is needed to remind both parties of this taken-for-granted whole (another infinity term), while confusion arises if explicit attention is not called to the fact that it is a very different sort of word from the definite terms of discourse which denote distinctions and their relations to one another. In the text, attention is called to the fact that the business man wrestling with a difficulty or a scientific man engaged in an inquiry finds his checks and control specifically in the situation in which he is employed, while the theorizer at large leaves out these checks and limits, and so loses his clews. Well, the words "experience," "situation," etc., are used to _remind_ the thinker of the need of reversion to precisely something which never can be one of the terms of his reflection but which nevertheless furnishes the existential meaning and status of them all. "Intuition," mysticism, philosophized or sophisticated monism, are all of them aberrant ways of protesting against the consequences which result from failing to note what is conveyed by words which are not terms. Were I rewriting these essays _in toto_ I should try to take advantage of these and other indispensable considerations advanced by Mr. Klyce; but as the essays must stand substantially as they were originally written, and as an Introduction to them must, in order to be intelligible, be stated in not incongruous phraseology, I wish simply to ask the reader to bear in mind this radical difference between such words as "experience," "reality," "universe," "situation," and such terms as "typewriter," "me," "consciousness," "existence," when used (as they must be used if they are to be terms) in a differential sense. The term "reality" is particularly treacherous, for the careless tradition of philosophy (a carelessness fostered, I am sure, by failure to make verbally explicit the distinction to which Mr. Klyce has called attention) uses "reality" both as a term of indifferent reference, equivalent to everything taken together or referred to _en masse_ as over against