"There are things that we know but cannot tell. This is strikingly true for our knowledge of skills. I can say that I know how to ride a bicycle or how to swim, but this does not mean that I can tell how I manage to keep my balance on a bicycle or keep afloat when swimming. I may not have the slightest idea of how I do this, or even an entirely wrong or grossly imperfect idea of it, and yet go on cycling or swimming merrily. Yet, it cannot be said that I know how to bicycle or swim and not know how to coordinate the complex pattern of muscular acts by which I do my cycling or swimming. It follows that I know how to carry out these performances as a whole and that I also know how to carry out the elementary acts which constitute them, but that, though I know these acts, I cannot tell what they are."
Polanyi M., Tacit Knowing: Its Bearing on Some Problems of Philosophy, Reviews of Modern Physics, 34 (4), Oct. 1962, 601-616.