It is worth while remembering that it is still an unaccepted one.

Most of his critics still consider it only Wordsworth's fun when he wrote: "One impulse from the vernal wood Can teach us more of man, Of moral evil and of good, Than all the sages can." Yet Wordsworth really believed that moral lessons and ideas were to be gathered from trees and stones.

It was the main part of his teaching.

He claimed that his own morality had been so furnished him, and he wrote his poetry to convince other people that what had been true for him could be true for them too.
For him life was a series of impressions, and the poet's duty was to recapture those impressions, to isolate them and brood over them, till gradually as a result of his contemplation emotion stirred again--an emotion akin to the authentic thrill that had excited him when the impression was first born in experience.

Then poetry is made; this emotion "recollected" as Wordsworth said (we may add, recreated) "in tranquillity" passes into enduring verse.