Whereas Robinson Jeffers had depicted the destructive course of human narcissism in Tamar, in Roan Stallion he turned to follow the path of human religion. In a nutshell, it is about a half-Indian woman, in several aspects a personification of California, whose religion is a hybrid of Catholic Christianity and horse worship. She comes to worship a stallion that in the end kills her husband. Though the death of her neglectful husband seems to be no great loss, she is compelled to kill the stallion—her God—ostensibly because it has killed a man. In doing so, California exhibits her faithfulness to her species. As such, she is no great Inhumanist. Though there is a white fire of God at the heart of her smoke-smothered mysticism, her striving for transcendence is nothing noble, but rather a selfish human flourish that is doomed to end in violent tragedy.
Early in the story, California has a vision of the baby Jesus draped in light. Later, she mentions the vision to her daughter, and speaking of the mother of Jesus, says (SP 124):
… The power, the terror, the burning fire covered her over …
The word power here is likely a hint at divinity. The phrase “covered her over” may possibly have a sexual connotation in this context, as there are references in the poem to a sexual relationship between Mary and God that California desires to re-enact with the stallion-god. As she saw Mary—bride of God—covered in fire, California also would be covered by fire (and by the stallion) at the eroto-mythological “climax” of the poem. California prostrates herself before the stallion and prays to it as though it were God. Suddenly nothing is there but a great fire. In the midst of the fire, human myths are born and myths die in a kind of orgasmic image-storm:
... The fire threw up figures
And symbols meanwhile, racial myths formed and dissolved in it,
the phantom rulers of humanity
That without being are yet more real than what they are born of,
and without shape, shape that which makes them:
The nerves and the flesh go by shadowlike, the limbs and the lives shadowlike,
these shadows remain, these shadows
To whom temples, to whom churches, to whom labors and wars,
visions and dreams are dedicate … (SP 130)
Just as sexual intercourse brings about the birth of biological creatures, this divine intercourse gives birth to myths. The scene ends with the fire burning in California’s mind (rather than her loins):
Figures and symbols, castlings of the fire, played in her brain;
but the white fire was the essence,
The burning in the small round shell of bone that black hair covered,
that lay by the hooves on the hill-top. (SP 131)
Is this “white fire” merely a fire of the human mind? It should go without saying that all this is occurring in California’s brain. That being a given, does this fire represent something more primal than the brain itself?
Jeffers elucidates upon this in Apology for Bad Dreams and also in a draft of a letter dated 5 November 1944, leaving little doubt that all the fire and shadows in her head were more akin to the shadows in Plato’s cave than anything representing enlightenment.
Just past the mid-point of the story, the poet had taken the stage to deliver a brief sermon that refers to what one must presume to be the self-same white fire:
Humanity is the mould to break away from, the crust to break through,
the coal to break into fire,
The atom to be split. …
Tragedy that breaks man's face and a white fire flies out of it; …
… for itself, the mould to break away from, the coal
To break into fire, … (SP 125)
This sounds a bit like Nietzsche (and with regard to tragedy, Schopenhauer). Here we present some Nietzsche for comparison:
I teach you the overman. Man is something that shall be overcome. … The overman is the meaning of the earth. Let your will say: the overman shall be the meaning of the earth! I beseech you, my brothers, remain faithful to the earth, and do not believe those who speak to you of otherworldly hopes!
— Thus Spoke Zarathustra 
Has California, then, overcome her humanity? Has she broken away from the mold? Her choice to shoot the stallion after it has killed Johnny tells us that she remains faithful to her species, regardless of her object of worship. Her religion, though full of fire and smoke and directed towards an inhuman animal, remains a human religion. She will even kill her God to retain her fidelity to her race. 
Is this a Nietzschean story? Only in a very restricted sense. The use of the stallion as God-manifestation renders this more truly a Jeffers story. Also, there is a sense of something universal here that Nietzsche may not have endorsed. Nietzsche tended to dislike universals. Jeffers speaks of his pantheistic God in a reverential tone, whereas Nietzsche speaks of a God who is dead (God being a stand-in for universals in general).
There are other poems in which Jeffers speaks of fire as a kind of primal essence. We have already cited verses from two short poems included with Tamar that serve as good examples of this. In The Tower Beyond Tragedy, published alongside Roan Stallion, the character Orestes speaks of having found Jeffers’ Nirvana:
... to go behind things, beyond hours and ages,
And be all things in all time, in their returns and passages,
in the motionless and timeless center,
In the white of the fire … (SP 113)
In this passage, Jeffers is not suggesting that the white of the fire is in anybody’s head. Evidently, his use of this construct is pantheistic, with the universe-entire represented by a fire and the divine, timeless core represented by the white of that fire.
Arthur Schopenhauer, it should perhaps be noted, famously argued that the great value of tragic poetry is in its power to lead the audience toward extinction of self (Nirvana):
We see in tragedy the noblest men, after a long conflict and suffering, finally renounce forever all the pleasure of life and the aims till then pursued so keenly, or cheerfully and willingly give up life itself. 
What is meant here by “giving up” is more a Buddhist (or even Islamic ) sense of surrender than corporeal suicide. Robinson Jeffers follows this model in The Tower Beyond Tragedy, arguably with an overdose of didacticism.