We must believe that "emotion recollected in tranquillity" is an inexact formula. For it is neither emotion, nor recollection, nor without distortion of meaning, tranquillity. It is a concentration, and a new thing resulting from the concentration of a very great number of experiences which to the practical and active person would not seem to be experiences at all; it is a concentration which does not happen consciously or of deliberation. These experiences are not "recollected" and they finally unite in an atmosphere which is "tranquil" only in that it is a passive attending upon the event.
T.S. (Thomas Stearns) Eliot (1888–1965), Anglo-American poet, critic. repr. In Selected Prose of T.S. Eliot, ed. Frank Kermode (1975). "Tradition and the Individual Talent," sect. 2, Egoist (London, September and December 1919).
See Wordsworth's comment under "poetry" for the original formulation of his theory of poetry.