“These observations show that strictly speaking nothing we know can be said precisely; and so what I call ‘ineffable’ may simply mean something that I know and can describe less precisely than usual, or even only very vaguely. … Although the expert diagnostician, taxonomist and cotton-classer can indicate their clues and formulate their maxims, they know many more things than they can tell, knowing them only in practice, as instrumental particulars, and not explicitly, as objects. The knowledge of such particulars is therefore ineffable, and the pondering of a judgment in terms of such particulars is an ineffable process of thought. This applies equally to connoisseurship as the art of knowing and to skills as the art of doing, wherefore both can be taught only by aid of practical example and never solely by precept.”
…
“It is not difficult to recall such ineffable experiences, and philosophic objections to doing so invoke quixotic standards of valid meaning which, if rigorously practised, would reduce us all to voluntary imbecility.”
Michael Polanyi, Personal Knowledge, 87-88.