Primarily an idea developed by the Hungarian social philosopher MICHAEL POLANYI (1891-1976).
Starting from such facts as our ability to recognize faces without knowing how we do so, and to be trained in a psychological laboratory to respond to certain perceived stimuli without knowing just what it is we are responding to, Polanyi claims that we transfer our attention from (for example) the specific features of a face to the face as a whole (we attend from the former to the latter, as he puts it), and thereby have tacit knowledge of the former.
The idea is then developed to account for the foreshadowing by which a scientist sees first a problem and then a possible solution to it in his data. The important point, however, is not whether the knowledge in question is unconscious, but its function in being that which we 'attend from'.
'Tacit knowledge' has also been used for our knowledge of what gives meaning to the words and sentences of our own language.
M Polanyi, The Tacit Dimension (1966), ch. 1