Critics and poets, in all ages and countries tried to explain their own theory and practice of poetry. Wordsworth, too, expounded his views on poetry, its nature and functions, and the qualifications of a true poet in his Preface to the Lyrical Ballads.

On the nature of poetry, Wordsworth states that:

“Poetry is the spontaneous overflow of powerful passion”.

Internal feelings of the poet proceeds poetry. It is a matter of feeling and temperament. True poetry cannot be written without proper mood and temperament. It cannot be produced to order. It must flow out freely and willingly from the soul as it cannot be made to flow through artificially laid pipes. Secondly, poetry is a matter of powerful feelings. It is never an intellectual process.

“Poetry is born not in the mind but in the heart overflowing with feelings”.

Poets are gifted with greater organic sensibility. They have greater ability to receive sense impressions. Beauties of nature, which may leave ordinary mortals untouched, excite poet’s powerful emotions and he feels an urge to express them. Wordsworth’s heart leapt up with joy on beholding a rainbow or daffodils dancing in the breeze and he expressed his overflowing feelings spontaneously in his immortal poems.

According to Wordsworth, good poetry is never an instant expression of powerful emotions. A good poet must meditate and ponder over them long and deeply. Poetry has its origin in “emotions recollected in tranquility”. Experience has to pass at least four stages before successful composition becomes possible. Firstly, there is the observation or perception to some object, character or event which sets up powerful emotions in poet’s mind. Secondly, there is recollection and contemplation of that emotion in silence. In this stage, memory plays a very important part. An interval of time must elapse, in which the first experience sinks deep into the poet’s insight and becomes his part and parcel. During the interval, the mind ponders and the impression received is purged of the unneeded elements or superfluities and is “qualified by various pleasures”. This filtering process is very slow; time and solitude are vital. Thus, the poet’s emotion is universalized. Thirdly, the interrogation of memory by the poet sets up, or revives, the emotion in “the mind itself”. It is very much like the first emotion, but is purged of all superfluities and constitutes a “state of enjoyment”.

This does not mean that the creative process is a tranquil one. The poet points out that in the process of contemplation, “tranquility disappears”. The poet has to “passion anew” while creating and is terribly exhausted as a result. But creation, if it be healthy, carries with it joy or “an over-balance of pleasure”. On the whole, “the mood of imaginative creation is enjoyment”. The ability to create comes from nature and not from premeditated art.

The fourth and last stage is of composition. The poet must convey that “overbalance of pleasure” and his own “state of enjoyment” to others. He differs from ordinary individuals in communicating his experience to others in such a way as to give pleasure. Metre is justified for it is pleasure super-added:

“Verse will be read a hundred times where Prose is read only once”.

Wordsworth himself closely followed his theory. He rarely made, “a present joy the matter of a song”. He did not poetize an experience immediately; his hardly ten poems are described unplanned. His composition had a wide interval between an experience and its poetic delineation. He had a powerful memory and at times he would fetch out an impression, “from hiding places ten years deep”. All his best poems resulted from emotions recollected in tranquility.

Recalling in silence enables the poet to see into the things deeply and converse the very soul of an experience to his readers. Through such contemplation the poet is able to impart to everyday object a ‘visionary gleam’, a ‘glory’, a ‘light that never was on land and sea’. As such recollection is best done in solitude, the poet loved lonely places, liked to wander all alone, lost in reverie, and was known by the rustics of Cumberland as the Solitary.

Wordsworth asserts that the function of poetry is to give pleasure. Even the painful subject should give pleasure. The poet in a “state of enjoyment” must commune this enjoyment to his readers. But pleasure is not the only and the chief aim of poetry. It is not an entertainment or a pastime. He tells:

“It is the breath and finer spirit of all knowledge, the impassioned expression that is in the countenance of all science”.

To be incapable of poetic feeling is to be without love of human nature and reverence of God. Its mission is to:

“Arouse the sensual from their sleep of Death. And win the vacant and the vain to noble Rapture”.

Poetry must serve the purposes of life and morality.

“Poetry divorced from morality is valueless”.

He hoped to console through his own poetry, the afflicted, to add sunshine to daylight, to lead the people to see, to think and to feel and become more virtuous.

Any subject can be poetically treated but Wordsworth favored incidents and characters from low and rustic life. He made the folks of Cumberland, their lives and objects of nature, the subjects of his poetry, for in rustic life the basic passions and emotions can be observed more clearly and expressed more perfectly. Such elementary passions in rural settings are linked with, “the beautiful and permanent forms of nature”. For Wordsworth it is the feeling and emotion that is important and not action and situation.

“Feeling developed in a poem gives importance to the action and situation and not the diction and situation to the feeling”.

Wordsworth's theory of poetic diction was a direct outcome of his democratic preference for simple rustic life and characters. When the theme was simple, the language must be simple too. It must be a selection of the language really spoken by such men otherwise it would not be in character. He is, therefore, critical of the artificial poetic diction of 18th century poetry.