I have said that poetry is the spontaneous overflow of powerful feelings: it takes its origin from emotion recollected in tranquillity: the emotion is contemplated till, by a species of reaction, the tranquillity gradually disappears, and an emotion, kindred to that which was before the subject of contemplation, is gradually produced, and does itself actually exist in the mind. In this mood successful composition generally begins, and in a mood similar to this it is carried on.
Wordsworth suggests that while the 'overflow of powerful feelings' that constitutes poetry is 'spontaneous', it is also, and at the same time, not spontaneous. The emotion is 'recollected' and 'contemplated', rather than immediately acted upon or written about. The 'origin' of poetry, therefore, is at one remove from the 'emotion' that the poet subsequently experiences and puts into words. But, in order to minimise this discrepancy, Wordsworth goes on to suggest that in fact the poetic act of contemplation itself produces an emotion. This emotion is both 'kindred' to the original and 'actually exist[s] in the mind'. In other words, the emotion produced in the act of contemplation is both a copy and itself original. In his complex, guarded, and finally contradictory analysis, then, Wordsworth seeks to explain poetry in terms of the author's experience or emotion and as a supplement to, or copy of, that experience or emotion.
Thus Andrew Bennett, writing on "Expressivity" in Literary Theory and Criticism: an Oxford Guide. Now, it's not that I think Bennett is wrong. Wordsworth is a little contradictory, if you're reading him as an amateur philosopher. But seeing this passage again in the context of Bennett's essay it struck me that this part of Wordsworth's "Preface" is not so much an attempt at analysis as a report from the field. Wordsworth is explaining his working technique - and today it occurred to me that this technique has a name.
William Wordsworth was a Method actor.