Professor Klein then speaks of "that artistic finish that we admire in Euclid's Elements," and mentions Allman's important historical work. I heartily concur in this estimate of Euclid, and desire to contrast it with the error of Charles S. Peirce, in the Nation, where he speaks of "Euclid's proof (Elements Bk. I., props. 16 and 17)" as "really quite fallacious, because it uses no premises not as true in the case of spherics." Our bright American seems to have forgotten Euclid's Postulate 6 (Axiom 12 in Gregory, Axiom 9 in Heiberg), "Two straight lines cannot enclose a space;" that is, two straights having crossed never recur.

Conceptual graphs are system of logic based on the existential graphs of Charles Sanders Peirce and the semantic networks of artificial intelligence. The purpose of the system is to express meaning in a form that is logically precise, humanly readable, and computationally tractable.

Ultimately, the last word is never ours. Peirce said: the meaning of my life is entrusted to others. [...] Which proves that truth is never something definitive; we are always mistaken. On a journey. It is no coincidence that I speak of the “transit of truth.”

One of the greatest philosophers of all time.

Beyond doubt ... he was one of the most original minds of the later nineteenth century and certainly the greatest American thinker ever.

Peirce was a man of tremendous energy, producing a multitude of ideas, good, bad, and indifferent. He reminds on of a volcano spouting vast masses of rock, of which some, on examination, turn out to be nuggets of pure gold. He holds―and I confess that an examination of scientific inference has made me feel the force of this view―that man is adapted, by his congenital constitution, to the apprehension of natural laws which cannot be proved by experience, although experience is in conformity with them.

Peirce held that the continuity of space, time, ideation, feeling, and perception is an irreducible deliverance of science, and that an adequate conception of the continuous is an extremely important part of all the sciences. This doctrine he called “synechism,” a word deriving from the Greek preposition that means “(together) with.”

James called Peirce the most original thinker of their generation; Peirce placed himself somewhere near the rank of Leibniz. This much is now certain; he is the most original and versatile of America's philosophers and America's greatest logician.

Peirce was concerned to explicate the idea of meaning whereas James was concerned to explicate the meaning of ideas.

The principle of interpretation says that "a sign is something by knowing which we know something more" (Peirce). The Peircean idea of semiosis is the idea of an infinite process of interpretation.