Let me not dare to attempt the definition of poetry, nor answer the question what it is. Like religion, love, nature, while those terms are indispensable, and we all give a sufficiently accurate meaning to them, in my opinion no definition that has ever been made sufficiently encloses the name poetry
Nor can any rule or convention ever so absolutely obtain but some great exception may arise and disregard and overturn 

The poetic area is very spacious—has so many mansions—has room for all—
An ensemble with measureless varieties, adopting countless samples and elements from all lands, all ages,
Limitless, subtle, refusing to be tabulated, needing comparisons and contrasts,
Evolutionary, and ready at any time for themes, standards, previously unknown.

The play of imagination, with the sensuous objects of nature for symbols, and faith—with love and pride as the unseen impetus and moving-power of all—make up the curious chess-game of a poem;
All that defines the road between conceivable objects and the human spirit, and explains what those objects mean, is poetry, coarse or fine.
This poetry, or aliment of the soul, we must have,
It is clamored for with the most irresistible longing, for we are greedy of this sort of  diet.

The points of union and rapport among all the poems and poets of the world, however wide their separations of time and place and theme, are much more numerous and weighty than the points of contrast.  
The verse of all tongues and ages, all forms, all subjects, really combine in one aggregate and electric globe or universe, with all its numberless parts and radiations held together by a common centre or verteber—in its entirety the dominant moral factor of humanity’s progress.

The great idea, that, O my brethren, that is the mission of poets.
In all times and in all nations it has been the faith of poets to believe in the noblest thoughts and deeds and to express them,
In this we inherit and partake of every one without distinction of place,
In this is the common glory of poets irrespective of period or place,
In this the good of any one is the good of all.
A great poem is for ages and ages in common, and for all degrees and complexions, and all departments and sects, and for a woman as much as a man, and a man as much as a woman.

The poets are divine mediums,
Through them come spirits and materials to all the people, men and women—
The spirit of life in visible forms,
The spirit of the seed growing out of the ground,
The spirit of the resistless motion of the globe.

Our visions, the visions of poets, the most solid announcements of any,
For we support all, fuse all,
After the rest is done and gone, we remain,
There is no final reliance but on us.

The words of true poems are the general light and dark,
They balance ranks, colors, races, creeds, and the sexes—

Divine instinct, breadth of vision, the law of reason, health, rudeness of body, withdrawnness,
Gayety, sun-tan, air-sweetness, such are some of the words.
I want for poetry the clear sun shining, and fresh air blowing—the strength and power of health, not of delirium, even amid the stormiest passions—with always the background of the eternal moralities. 

The great poets are to be known by perfect personal candor,
Perfect transparent clearness, sanity, and health are 
Rule in all addresses and poems and other writings: Make it plain,
Do not undertake to say anything, however plain to you, unless you are positive you are making it perfectly plain to those who hear or read,
Nothing will do, not one word or sentence, that is not perfectly clear, with positive 

Was’t charged against my chants they had forgotten art?
The lyrist’s measur’d beat, the wrought-out temple’s grace—column and polish’d arch forgot?
The art of art, the glory of expression, and the sunshine of the light of letters is simplicity,
The poetic quality blooms simple and earnest as the laws of the world—
No puns, funny remarks, double entendres, ironies, sarcasms,
Nothing splendid or pretty or startling or new or talented,
But honest truths.
If they are at the roots, there is a live growth; else all is of no avail.

Only that which is simply earnest, unadorned, unvarnished, laconic, taciturn, preserves perfect calmness and sanity.
Lumber the writing with
Let it go as lightly as a bird flies in the air, flow on unhasting and unresting as a fish swims in the ocean,
That is the divine style—O if it can be attained!

The great poets are also to be known by the absence in them of tricks,
The style of expression must be carefully purged of anything striking or dazzling or ornamental, and with great severity precluded from all that is eccentric.
Too much attempt at ornament is the blur upon nearly all literary styles,
(I was born in the vesture of this false notion of literature;
I pride myself I have escaped the pollution as much as any,)
Anything is most beautiful without ornament.
Especially no ornamental adjectives, unless they have come molten hot, and imperiously prove themselves,
No ornamental similes at all, not one—be faithful to the perfect likelihoods of nature—
No quotations, and no reference to any other writers,
No illustrations whatever from the ancients or classics, nor from mythology, nor from the royal and aristocratic institutions and forms of Europe.

In these “Leaves” nothing is poetized,
(I had great trouble in leaving out the stock “poetical” touches—but succeeded at last,)
Nothing for beauty’s sake, no euphemism, no
The audible rhyme soon nauseates, the inaudible rhyme is delicious without end.
The rhyme and uniformity of perfect poems show the free growth of metrical laws, and bud from them as unerringly and loosely as lilacs and roses on a 
What I experience or portray shall go from my composition without a shred of my composition.

I will not have in my writing any elegance or effect or originality to hang in the way between me and the rest like curtains. I will have nothing hang in the way, not the richest curtains.
What I tell I tell for precisely what it is—exact, simple, no twistified or foggy sentences at all,
Everything is literally photographed—the most translucid clearness without 
I send no agent or medium, I offer no representative of value, but offer the value itself.

The basis of the “Leaves,” differing I suppose from many grandest poets, was and is that I find everything in the common concrete—the flesh, the common passions, the tangible and visible, etc.—and in the average, the common and general road.
I radiate, work from these outward;
Or rather, hardly wish to leave here, but to remain and celebrate it all.

Is there any other poem of the sort extant—or indeed hitherto attempted?
I will be the originator, the inventor.
Yes, it is a new style, of course,
But that is necessitated by new theories, new themes—or say the new treatment of themes—
How much more agreeable to me is the conversation or writing that does not take hard paved tracks, the usual and sterotyped, but has little peculiarities and even kinks of its own, making its genuineness—its vitality.

You may start at the style; people resent anything new as a personal insult,
(When umbrellas were first used in England, those who carried them were hooted and pelted so furiously that their lives were endanger’d,) 
But every really new person, (poet or other,) makes his style—sometimes a little way removed from the previous models—sometimes very far removed.

I have not only not bother’d much about style, form, art, etc., but confess to more or less apathy (I believe I have sometimes caught myself in decided aversion) toward them throughout, asking nothing of them but negative advantages—that they should never impede me, and never under any circumstances, or for their own purposes only, assume any mastery over me.

Has it never occurred to anyone that the real tests applicable to a book lie entirely outside of literary tests?
The words of true poems do not merely please,
As, within the purposes of the cosmos, there is a moral purpose certainly underlying all—so in the product of the greatest literatus. This is the last, profoundest measure and test.

First to me comes the people, and their typical shape and their attitudes,
Then the divine minor, literature—
The person is the spinal matter in books, in art;
The highest art is not to express art, but to communicate life. 
No one will get at my verses who insists upon viewing them as a literary performance, or attempt at such performance, or as aiming mainly toward art or aestheticism.

Still the final test of poems, or any character or work, remains—
Has it help’d any human soul?
How far can it elevate, enlarge, purify, deepen, and make happy the attributes of body and soul?
It should nourish with joy the pride and completion of man in himself.

These are the things made the themes of “Leaves of Grass.”
The book is the product of that sense of cosmical beauty, of which even literature is but a fraction,
And of the largest universal law and play of things—
The play of law in the outside world and the play of passion and spirit in the human soul—
To give full utterance to power, often inexplicable, in the universe and in man.
Poetry will be revivified by this tremendous innovation, the cosmic spirit, which must henceforth be the background and underlying impetus, more or less visible, of all first-class songs,
Not to be construed as an intellectual or scholastic effort or poem mainly, but more as a radical utterance out of the emotions and the physique.

I have in view an effect which I clearly feel, but cannot as clearly define,
A book separate, not link’d with the rest, nor felt by the intellect,
Effect upon the reader not as much intellectual as moral. 
Neither can “Leaves of Grass” ever be judged by the intellect,
This strange song (often offensive to the intellect) is to be felt, absorbed by the soul,
To swim the sea, the air, with joy with you, O soul of man,
It shall pass by the intellect,
But you ye untold latencies will thrill to every page.

Neither can “Leaves of Grass” suffice to be read merely once or so, for amusement;
It is to be dwelt upon, returned to, again and again,

Needs study, and more than one perusal, to give up its meaning and confer pleasure,
(First rate poems never immediately gratify,) 
Wants a broad space to turn in, like a big ship.