Abstract
Zeng Tiancong (1910-2007) was one of the major Taiwanese philosophers in the period of Japanese rule, though his philosophy has since been neglected. In this article I will focus on his main philosophical work, Theory of the Principle of Truth (published in 1937), in which he opens an alethiological field of inquiry and creates a theory of the principle of truth, which serves as a basis for his own philosophical system. In order to understand and evaluate his contribution to philosophy, it is important to clarify his explication of ＂truth-in-itself.＂ It is my view that his entire philosophical career served to illuminate this thesis. But his plan was left unfinished, obscuring some of his creative ideas and philosophical concepts. In this article I will focus on the inquiry into ＂truth-in-itself＂, to clarify its ＂pure eidos.＂ My primary aim is to shed light on Zeng's insight, by explicating his concepts and reinforcing his arguments.