At its core, the philosophy known as American Transcendentalism is the belief in an ideal spiritual state that “transcends” the physical. This state can only be realized through an individual's intuition. It cannot be achieved through organized religion (or any religion).
The tenets of American Transcendentalism were articulated by Ralph Waldo Emerson, (the man often identified as the “father” of American Transcendentalism) in his 1841 essay, “The Oversoul.”
There are four major themes in “The Oversoul”:
1. The existence and nature of the human soul.
[T]he soul in man is not an organ, but animates and exercises all the organs; is not a function, like the power of memory, of calculation, of comparison, but uses these as hands and feet; is not a faculty, but a light; is not the intellect or the will, but the master of the intellect and the will; is the background of our being, in which they lie, — an immensity not possessed and that cannot be possessed. From within or from behind, a light shines through us upon things, and makes us aware that we are nothing, but the light is all.
2. The relationship between the soul and the personal ego.
As with events, so is it with thoughts. When I watch that flowing river, which, out of regions I see not, pours for a season its streams into me, I see that I am a pensioner; not a cause, but a surprised spectator of this ethereal water; that I desire and look up, and put myself in the attitude of reception, but from some alien energy the visions come.
3. The relationship of one human soul to another.
Childhood and youth see all the world in them. But the larger experience of man discovers the identical nature appearing through them all. Persons themselves acquaint us with the impersonal. In all conversation between two persons, tacit reference is made, as to a third party, to a common nature.
4. The relationship of the human soul to God.
If we will not interfere with our thought, but will act entirely, or see how the thing stands in God, we know the particular thing, and every thing, and every man. For the Maker of all things and all persons stands behind us, and casts his dread omniscience through us over things.
Casy come very close to articulating the major points of Emerson’s philosophy. When he first meets Tom, who is walking home after a stint in prison, Casy explains the first steps on his new path:
"I was a preacher," said the man seriously. "Reverend Jim Casy—was a Burning Busher. Used to howl out the name of Jesus to glory. And used to get an irrigation ditch so squirmin' full of repented sinners half of 'em like to drowned. But not no more," he sighed. "Jus Jim Casy now. Ain't got the call no more. Got a lot of sinful idears—but they seem kinda sensible."
Tom tries to cajole Casy, telling him how fondly his family recalled his preaching, but the man is not moved. He replies:
"I ain't preachin' no more much. The sperit ain't in the people much no more; and worse'n that, the sperit ain't in me no more. 'Course now an' again the sperit gets movin' an' I rip out a meetin', or when folks sets out food I give 'em a grace, but my heart ain't in it. I on'y do it 'cause they expect it."
“Before I knowed it, I was sayin’ out loud, “The hell with it! There ain’t no sin and there ain’t no virtue. There’s just stuff people do. It’s all part of the same thing. And some of the things folks do is nice and some ain’t nice but that’s as far as any man got a right to say.”
As he continues to verbalize his feelings, perhaps for the first time, Casy arrives at this conclusion:
“Why do we got to hang it on God or Jesus? Maybe,” I figgered, “’maybe it’s all men an’ all women… all men got one big soul and ever’body a part of. Now I sat there thinkin’ it, and all of a suddent- I knew it. I knew it so deep down it was true, and I still know it.”