Selection from C.S. Peirce, “Some Amazing Mazes, Fourth Curiosity” (c. 1909)
Of triadic Being the multitude of forms is so terrific that I have usually shrunk from the task of enumerating them; and for the present purpose such an enumeration would be worse than superfluous: it would be a great inconvenience. In another paper, I intend to give the formal definition of a sign, which I have worked out by arduous and long labour. I will omit the explanation of it here.
Suffice it to say that a sign endeavors to represent, in part at least, an Object, which is therefore in a sense the cause, or determinant, of the sign even if the sign represents its object falsely. But to say that it represents its Object implies that it affects a mind, and so affects it as, in some respect, to determine in that mind something that is mediately due to the Object. That determination of which the immediate cause, or determinant, is the Sign, and of which the mediate cause is the Object may be termed the Interpretant.
C.S. Peirce, Collected Papers, CP 6.347
Peirce, C.S., Collected Papers of Charles Sanders Peirce, vols. 1–6, Charles Hartshorne and Paul Weiss (eds.), vols. 7–8, Arthur W. Burks (ed.), Harvard University Press, Cambridge, MA, 1931–1935, 1958. Volume 6 : Scientific Metaphysics, 1935.