The reason I know that the water is rippling is because I am not making it ripple, for I do not ripple. Therefore it must be rippling on its own accord. Whether it is rippling as I see it may be wrong, but I atleast know that I am not making it ripple. The Eternal Tao is the essence which is unknowable and inconceivable, however the natural Tao is the part of that Tao that does allow us to know it, even if partially. It is not a division of reality, only the part of that reality that we can concieve. This makes it no less real than the Eternal Tao, but simply is the part of the Tao we know about. And the natural Tao is that the water is rippling. The Eternal Tao is the inconcievable essence which created the water, the ripples, and everything. And from the understanding of the self, and knowing that we do not ripple, we come to the understanding that the rippling is happening on its own accord without our influence. Therefore, we know that we do not ripple with it. Whether or not what we are percieving as rippling is completely true or not in the outside world has no relevance. For we still know that whatever is happening outside of ourselves, is indeed outside of ourselves for we know ourselves truly enough to know that we do not "ripple." But the fact that the water may or may not be rippling in true reality had nothing to do with the question. The question was only to allow you to understand yourself enough to know that the water is rippling on its own accord, for it is not in your nature to ripple.
So to clear this up... I know for sure (self) that I do not ripple. Therefore, the water rippling (natural Tao) is indeed happening as such outside of me. And since I am indeed percieving it as such, and perception is not the one true reality (Eternal Tao), why, if, or how the water is rippling is not based on my perception, but my self understanding. Therefore, I know myself (the whole point of the question) and I know I do not ripple.