Five years have past; five summers, with the length
Of five long winters! and again I hear
These waters, rolling from their mountain-springs
With a sweet inland murmur.—Once again
Do I behold these steep and lofty cliffs,
Wordsworth’s “Tintern Abbey” opens with the speaker’s declaration that five years have passed since he last visited this location, encountered its tranquil, rustic scenery, and heard the murmuring waters of the river along with the lofty cliffs.
The speaker doesn't open with a description of the view or even an explanation of where he is, he starts by telling us how much time has passed since he was last here (and we know from the title that "here" is "a Few Miles above Tintern Abbey," on the "Banks of the Wye"). He doesn't just say "five years have past," he really emphasizes that five years is a very long time by adding up the seasons, especially the "five long winters." But now he's there again! So, "once again," the speaker can hear and see all the beautiful stuff that he remembers from his first visit. This is where he starts to describe those impressions, and he starts with what he can hear: the sound of the "mountain-springs." The "steep and lofty cliffs", are just as he remembered, too. He uses the word "again" in these lines, as well, to reinforce the idea that he's been here before.
The very first lines introduces that the subject of “Tintern Abbey” is memory—specifically, childhood memories of communion with natural beauty. “Tintern Abbey” is the young Wordsworth’s first great statement of his principle (great) theme: that the memory of pure communion with nature in childhood works upon the mind even in adulthood, when access to that pure communion has been lost, and that the maturity of mind present in adulthood offers compensation for the loss of that communion—specifically, the ability to “look on nature” and hear “human music”; that is, to see nature with an eye toward its relationship to human life.
For I have learned
To look on nature, not as in the hour
Of thoughtless youth; but hearing oftentimes
The still, sad music of humanity,
Nor harsh nor grating, though of ample power
To chasten and subdue.
And I have felt
A presence that disturbs me with the joy
Of elevated thoughts; a sense sublime
Of something far more deeply interfused,
Whose dwelling is the light of setting suns,
And the round ocean and the living air,
And the blue sky, and in the mind of man;
In this section of Wordsworth’s “Tintern Abbey” the speaker acknowledges that he is different now from how he was in those long-ago times, when, as a boy, he “bounded o’er the mountains” and through the streams. In those days, he says, nature made up his whole world: waterfalls, mountains, and woods gave shape to his passions, his appetites, and his love. That time is now past, he says, but he does not mourn it, for though he cannot resume his old relationship with nature, he has been amply compensated by a new set of more mature gifts.
Clearly, he has gained something in return: “other gifts have followed; for such loss… for I have learnt to look on nature, not as in the hour of thoughtless youth; but hearing oftentimes the still, sad music of humanity”. This is a philosophic statement about maturing, about the development of personality, and of the poetic or philosophic mind as well. So now the poet is able to feel a joy of elevated thought, a sense sublime, and far more deeply interfused. He feels a sense of sublime and the working of a supreme power in the light of the setting sun, in round oceans and in the blue sky. He is of opinion that a motion and a spirit impel all thinking things. Therefore Wordsworth claims that he is a lover of the meadows and of all which we see from this green earth. Nature is a nurse, a guide and the guardian of his heart and soul.
The poet comes to one important conclusion: for all the formative influences, he is now consciously in love with the nature. He has become a thoughtful lover of the meadows, the woods and the mountains. Though his ears and eyes seem to create the other half of all these sensations, the nature is the actual source of these sublime thoughts.