Wordsworth preface to the second edition of the Lyrical Ballads, he sets fourth his aims: The principal object proposed in these poems was to choose incidents and situations from common life, and to relate or describe them throughout in a selection of the language really used by men and at the same time to know over them a
certain coloring of the imagination whereby ordinary things should be presented to the mind in an unusual aspects. He goes on to say that humble and rustic life was generally chosen because in that condition the essential passions of the heart find a better soil. In which they can attain their maturity, realism under restraint and speak a plainer and more emphatic language, In the above statement we get some important points regarding Wordsworth's theory of poetic diction.
Firstly, in the choice of subjects or themes Wordsworth goes straight to common life and by preference to humble and rustic life.
Secondly, Wordsworth describes his themes taken from humble and rustic life as far as possible in a selection of language actually used by ordinary men. He does not look with favor upon the pompous and stilted circumlocution of the eighteenth century writers who delighted in using gaudy language.
Thirdly, Wordsworth says that while choosing his themes from common and rustic life and describing them in the language of the common people, his object to throw over them a certain coloring of the imagination, whereby ordinary things should be presented to the mind in an unusual aspect.