Jory, thanks for the link. I have met Endo sensei many times through the years, and discussed many things with him, but I was not aware that he has pondered the Tao Te Ching so deeply. Now I know what to discuss with him next time we meet.
Tao of Lao Tzu and Do of Japanese thought have similarities, but also substantial differences. I lack the knowledge to discuss those matters at any depth, but maybe we can convince Peter Goldsbury to say something about it?
My impression of Tao according to Lao Tzu is a sort of <I>primus motor</I> of the universe and everything in it. The primal natural law. Do in Japanese thought, on the other hand, is more personal. One's way towards fulfillment of one's potential.
So, using Tao in aikido practice is not simply putting emphasis on the last syllable of the name of the art, but viewing it from another angle altogether. A Taoistic approach needs to look at what happens on the tatami from far beyond it, contemplating what marks the patterns of the training make on the world as a whole - which should be as minute as ever possible, and thereby have the most power to cause a change for the better...