secern		to discriminate in thought.
alethiology		the branch of logic dealing with truth and error.
agnoiology		(arch.) the philosophical study of human ignorance.
haecceity		that which makes something uniquely what it is.
quiddity		the essential nature of a thing; a distinction subtle to the point of insignificance.
compossible		consistent.
antinomy		a contradiction between two laws, or between two statements arrived at through logical reasoning.
elenchus		a logical refutation, particularly by reducing to a contradiction; a false refutation.
porism		"(Math.) a form of proposition among the Greeks which has been variously defined, esp. a proposition affirming the possibility of finding such conditions as will render a certain problem indeterminate, or capable of innumerable solutions."
misology		a distrust or dislike of reasoning.
organon		a system of principles for philosophical investigation; an instrument of thought.
omphaloskepsis		navel-gazing.