For 10 points, identify this philosophical doctrine which argues against the possibility of reliable knowledge.
The second section of the third chapter of Robert Nozick's Philosophical Explanations is devoted to an analysis of this doctrine. Peter Unger wrote a book entitled Ignorance which purports to make a case for this philosophical doctrine, while an article by G.E. Moore that analyzes Russell's approach to this doctrine is titled after "Four Types of" it. Ancient exponents of this doctrine included Arcesilaus and Carneades, heads of the Academy who critiqued the "cataleptic impression" which formed the basis for Stoicist epistemology, as well as Pyrrho of Elis, who gives his name to another form of this doctrine. A book which asserts that "philosophy begins in medias res", was written by George Santayana to present a contrast between this doctrine and "animal faith". For 10 points, identify this philosophical doctrine which argues against the possibility of reliable knowledge.
The second section of the third chapter of Robert Nozick's Philosophical Explanations is devoted to an analysis of this doctrine.
skepticism