[freebeard]

Thanx. Similar to Carl Sagan: "Extraordinary events require extraordinary evidence."

Among the contributions of the Port-Royal Logic is the introduction of a distinction between comprehension and extension, which would later become a more refined distinction between intension and extension.[1] Roughly speaking: a definition with more qualifications or features (the intension) denotes a class with fewer members (the extension), and vice versa. The main idea traces back through the scholastic philosophers to Aristotle's ideas about genus and species,[2] and is fundamental in the philosophy of Leibniz.[3] More recently, it has been related to mathematical lattice theory in Formal Concept Analysis, and independently formalized similarly by Yu. Schreider's group in Moscow,[4] Jon Barwise & Jerry Seligman in Information Flow,[5] and others.

en.wikipedia.org/wiki/Port-Royal_Logic