Selections from C.S. Peirce, “Lowell Lectures of 1903”, CP 1.343–349
343. We may say that the bulk of what is actually done consists of Secondness — or better, Secondness is the predominant character of what has been done. The immediate present, could we seize it, would have no character but its Firstness. Not that I mean to say that immediate consciousness (a pure fiction, by the way), would be Firstness, but that the quality of what we are immediately conscious of, which is no fiction, is Firstness.
But we constantly predict what is to be. Now what is to be, according to our conception of it, can never become wholly past. In general, we may say that meanings are inexhaustible. We are too apt to think that what one means to do and the meaning of a word are quite unrelated meanings of the word “meaning”, or that they are only connected by both referring to some actual operation of the mind. Professor Royce especially in his great work The World and the Individual has done much to break up this mistake.
In truth the only difference is that when a person means to do anything he is in some state in consequence of which the brute reactions between things will be moulded [in] to conformity to the form to which the man’s mind is itself moulded, while the meaning of a word really lies in the way in which it might, in a proper position in a proposition believed, tend to mould the conduct of a person into conformity to that to which it is itself moulded.
Not only will meaning always, more or less, in the long run, mould reactions to itself, but it is only in doing so that its own being consists. For this reason I call this element of the phenomenon or object of thought the element of Thirdness. It is that which is what it is by virtue of imparting a quality to reactions in the future.
— Charles S. Peirce, “Lowell Lectures of 1903”, III, vol. 1, 3rd Draught. (CP 1.343)