Entering the era of 21st century, there are two characteristics bearing on thinkinginnovation and comprehension. As to innovation, how to exite creative-thinking is a warm problem. From the high level of philosophy—epistemology and relative-truth of materialist-dialectics, this paper shows that there is the duality of every form of thinking including the thinking of deduction and that of socalled fixed-accustoming. There is an existence of both non-creative thinking and creative thinking and under certain conditions non-creative thinking may be turn into creative thinking which can make new knowledge and innovative achievements. As to comprehension, there are many different opinions on how to define and classify thinkings. By combining physiology and psychology, this paper divides thinkings into 2 parts and 7 basic forms. Connecting dialectics with comprehension, the conclusions of this paper are shown： the duality of non-creative thinking and creative thinking, the duality of reasoning thinking and understanding thinking, the duality of original knowledge and new knowledge, the duality of idea and test-verification, the duality of discovery and invention, the duality of science (sense of truth ) and art (sense of beauty ). The last conclusion is expressed as an example of seeking the theory of a cross-course —industrial design, the main contents of which are technology, art and market. This theory of ID is the first advance in ID.