I get you. when you look at Chinese culture and the culture of the world in general, various philosophies and schools of thought have been intertwined and built upon each other it is impossible to figure out who did or said what first. I think what master yang said is a good way to look at it. it avoids too much pondering and enables the practitioner to get to the heart of the matter. (almost like clearing ones mind of too much dogma when following a religion. but hey that may be a horse of a different color. hope i didn't strike a vein there...sorry
) but i firmly believe Tai chi is based on the book of changes which is hands down one of China's oldest and most influential texts and the Taoist have revolved around that among other things over the centuries. maybe they didn't invent Tai chi maybe they did but i believe their contribution to it is undeniable. but like i said these things can be discussed and disputed forever. This may be for a different topic but i thought i would share it anyways it is from a site by a guy called Peter Lim (I think) about his summary on Wu Tunan's Interview with Chen Xin at Chen Village. You may have read this before if not very enlightening
"Wu Tu Nan visited the Chen Villiage in 1917. There were few educated people in the villiage at the time and he was directed to meet Chen Xin, this was before Chen Xin's book was published. Chen Xin was very frank in his interview with Wu Tu Nan and gave him an account of how Taijiquan came to the Chen Villiage . He said that both Taijiquan and the indigenous Chen family Pao Chui was practiced in the villiage but that Taijiquan came down from Jiang Fa. He also introduced Wu to Du Yu Wan who practiced Taijiquan and who said his art came down from Jiang Fa who was of the Wudang lineage, Du's subsequent book on Taijiquan in 1935 confirms this view and the authenticity and accuracy of Wu Tu Nan's interview material.
Chen Xin had told Wu that he was writing a book on Taijiquan. Wu then asked Chen Xin whether he practiced Taijiquan. Chen Xin replied that his father had let his older brother learn martial arts but had made him get an education instead so he did not know any martial arts. Wu then asked how he was going to write a book on martial arts if he did not practice martial arts. Chen replied that Taijiquan is based on the Book of Changes and that he felt that as long as an art conformed to the Book of Changes it was Taijiquan. So he intended to use the boxing postures of Pao Chui and relate them to the Book of Changes and that his purpose of the book was to show how the Book of Changes was related even to martial arts, it was not his intention of writing a martial arts manual...."