Plato’s ‘Academy’ has switched its philosophical position from dogmatism to skepticism in the third century B.C. And it has not changed its skepticism for the next hundred years until Antiochus of Ascalon ended it, and brought dogmatism back into the Academy. The purpose of the paper is two-fold: Firstly, when did Antiochus change his philosophical allegiance from skepticism to dogmatism? Historians have traditionally proposed that the breakup and falling-out between Antiochus and Skeptic Academy happened in 87/86 B.C. However in this paper I would suggest that it happened a few years earlier than the traditional interpretation. Secondly, whether his thought is compatible with that of the founder of the School, Plato? By virtue of discussing Antiochus’s epistemology and ethics, I would like to show that his Academic philosophy is quite different from Plato’s. In addition to the abovementioned two issues, the discussions of Antiochus’s thought in this paper can provide us a rather unusual way of looking at the development of ancient Greek philosophy.