One of Oppen's earliest and most lasting influences was the nineteenth century Romantic poet Perce Bysshe Shelley. Oppen owned a copy of the Modern Library collected edition of the works of Shelley and John Keats, and he refers to Shelley's works throughout his career, from "the rooms / Of Keats and Shelley" in Oppen's poem "Boy's Room," to the Shelley poems "Ode to the West Wind" and "Ozymandias," to Shelley's essay on poetics "A Defence of Poetry" in his essay "The Mind's Own Place" (whose title derives from Shelley's quotation of Milton and which seems in part to be a response to Shelley's essay), to a letter describing his visit Cambridge University at sixteen, "keeping my own council, of course, but wondering to myself, to begin with, I might survive to be an adult, and second if I would ever walk scholarly past those windows. I thought the chances slight. And the need to walk musing and scholarly and at the same time to have been sent down as befitted a Romantic, O wind, I thought, if winter ever
comes . . .," the concluding lines of course quoted from Shelley's "Ode to the West Wind." 
As with his more contemporary influences, Maritain and Camus, Oppen shares several biographical similarities with Shelley, of which Oppen was undoubtedly aware. Shelley, like Oppen, was born to wealth he would later rebel against and reject, at the same time he would live on family money (an allowance in Shelley's case, a family trust in Oppen's). Both attended private schools and had early run-in's with authority, be they school headmasters or classmates. Both had interrupted university careers (Shelley by publishing a pamphlet on atheism, Oppen by refusing to return to college after having met Mary) that widened an already unsurpassable rift between themselves and their fathers. Both eloped at the age of eighteen and would live primarily restless, nomadic lifestyles. They would also share a concern for the poor and oppressed; Shelley would contribute pamphlets on various social matters while Oppen would take a more active role as member of the Communist Party. Like Oppen, albeit from an idealistic perspective untarnished by the disasters of the twentieth century radical politics, Shelley came under the influence of socialism. His early poems "Queen Mab" and "The Mask of Anarchy" advocate revolution and radical reformism of existing political and religious institutions; Shelley's long poem Prometheus Unbound argues that men and women are the cause of these social inequities and therefore reform consists of individual moral responsibility. Where Shelley called for "universal regeneration by an apocalypse of the moral imagination," Oppen was living in the aftermath of this apocalypse; his Shelleyan (and Heideggerean) task therefore consisted of continued call for universal regeneration (most definitively in his poem "Leviathan"). Perhaps most importantly, Shelley and Oppen both possessed a belief in the limits of knowledge and refused to allow their artistic intuitions to harden into philosophical doctrine.
A key text among Shelley’s writings for Oppen is his 1821 essay "A Defence of Poetry." Shelley's essay comprises a surprising number of similar themes explored by Oppen, particularly Heidegger’s role of the poet as the "caretaker of being," and insists the importance of the imagination over reason, observing that
[reason] may be considered as mind contemplating the relations borne by one thought to another, however procured, [imagination], as mind acting upon those thoughts so as to colour them with its own light, and composing from them, as from other elements, other thoughts, each containing within itself the principle of its own integrity. The [imagination] is the [making], or the principle of synthesis, and has for its objects those forms which are common to universal nature and existence itself; [reason] is the [calculating] or principle of analysis, and its action regards the relation of things, simply as relations; considering thoughts, not in their integral unity, but as the algebraical representation which conduct to certain general results. Reason is the enumeration of quantities already known; imagination is the perception of the value of those quantities, both separately and as a whole. Reason respects the differences, and imagination the similitude of things. Reason is to Imagination as the instrument to the agent, as the body to the spirit, as the shadow to substance [emphasis mine].
This passage helps to illustrate a key theme in Oppen’s poetry: namely, the equation of the imagination, or more specifically, the poetic imagination with "existence itself"; Shelley states that "poetry is connate with the origin of man."  Compare this with Heidegger's conclusion that “language can only have arisen from the overpowering, the strange and the terrible, through man’s departure into being. In this departure language was being, embodied in the word: poetry. Language is the primordial poetry in which a people speaks being."
 As an act of creation, Shelley argues, the poet's imagination, actively "composes" originary thought, carrying with it "the principle of its ingenuity" and not "the enumeration of quantities already known," or, as Oppen states in his letter to his sister, explaining why he could not bring himself to write specifically political poetry, "any statement already determined before the verse" (SL, 20).
Shelley's essay has resonances with Heidegger's concept of the philosopher (and poet) as questioner, with the necessity of escaping the trappings of metaphysical tradition and returning to the "overpowering, the strange, the terrible," of the poet's primitive response to the world, what Oppen calls in a letter "an 'instant archeology' that imagines a personification of things already known, one imagines the first objects to become object to living consciousness - - their force in that among sensations they emerged as objects ---- can we suppose, in the history of the Sacred, a greater moment? This is the ground the poems meant to stand on. And to speak from." Illustrating this theme, Oppen’s aptly titled poem "Primitive" can be interpreted as a Vicoesque or Hegelian rendering of human consciousness awakening from the dream of myth "Screaming in terror," "Crying in nightmare / Of loss," to the nightmare of reality Oppen represents with ubiquitous human possessions ("a wash tub, / The delicate fish lines / His fingers know so well"), those familiar objects "visible in the clear night." 
It was Heidegger as a thinker that would have the most prominent and lasting influence on Oppen; his elucidation of being was an intricate and problematic influence on the development of Oppen's mature poetics. However, Oppen's understanding of Heidegger was, at best, extremely personal and deeply flawed. The implications of Heidegger's philosophy is explored in The Materials and significantly broadened by This In Which, where the influence is most deeply felt, particularly Heidegger's concept of "disclosure," that is, the disclosiveness of being through objects where being is felt most powerfully in what Oppen calls the "fusion of subject and object" where the poet (subject) and the world (object) together produce what Oppen calls a "cadence of disclosure."
Oppen's Heideggerean project is a return to the non-predicative "is" of these objects; as he explains in a letter, "'their power in that among sensations they emerged as objects' . . . To reverse that process; bored by objects to wish to convert them to symbols of interior sensations, interior movements - - is boredom indeed! . . . if we still possessed the word 'is,' there would be no need to write poems." This return to the originary, the primitive, to the predicative "is" of objects revitalizes and opens perception to the world. As Oppen concludes: "One inch above, one inch below what has already been said – the world opens up" (SL, 248-9). Reason, as Shelley notes, can only provide "the relation of things," the everyday world, the "daylight" of "A Narrative" "In which things explain each other, / Not themselves" (NCP, 151).
Poets, Shelley observes, are able through their "vitally metaphorical" language, to see the "unapprehended relations of things," a perception that precedes the "classes of thoughts." Without the poets, Shelley declares, "language will be dead." Since Heidegger (and by extension, Oppen), believes language to be synonymous with consciousness and therefore being itself, Shelley's words have ominous implications, at the same time they illustrate the integral position of the poet, which Heidegger interpreted as the care of being through the care of language.
Shelley would call poets the "unacknowledged legislators of the world," for, in "the infancy of society every author is necessarily a poet, because language itself is poetry."  Had poets "never existed," Shelley wonders "what would have been the moral condition of the world?" Without poets, he argues, "the human mind could never, except by the intervention of these excitements, have been awakened to the invention of the grosser sciences, and that application of analytical reasoning to the aberration of society, which it is now attempted to exalt over the direct expression of the inventive and creative faculty itself" which "is the basis of all knowledge."
Shelley's prescription that the "cultivation of poetry is never more to be desired than at periods when, from an excess of the selfish and calculating principle [i.e. Oppen's Marxism], the accumulation of the materials of external life exceeds the quantity of the power of assimilating them to the internal laws of human nature" [emphasis mine]. Oppen may have had this passage in mind when looking for a title for his first book following his return to poetry, and the insistence in returning to the non-predicated object, shedding himself of the unwieldy exoskeleton of an habitual Marxism: "Poetry has to be protean," Oppen declares, "the meaning must begin there. With the perception" (SL, 20).
A similar thread is taken up by Shelley in his "Defence"; poetry, writes Shelley, is "the root and blossom of all other systems of thought."  It returns us to the non-predicative perception where "all things exist as they are perceived; at least in relation to the percipient." Here Shelley turns to that ultimate solipsist, Milton's Satan. Shelley laments Satan's acceptance of his position in life, arguing that "poetry defeats the course which binds us to be subjected to the accident of surrounding impressions." Poetry, he argues, "creates for us a being within our being. It makes us inhabitants of a world in which the familiar world is chaos."  Shelley interprets this as meaning that the poets as "hierophants of an unapprehended inspiration" makes them the "unacknowledged legislators of the world," thereby initiating a call-to-arms for poets to break free and to help others break free from the limitations of their age (Blake's "mind forg'd manacles" of church and state) and, unlike Milton's
Satan, not accept their lot in life but to envision or create a better world, if not for the present, then at least for future generations.
Oppen, writing from the perspective of having had his utopian revolutionary dream shattered by the cruel indifference of history, could not bring himself to accept such an overtly political interpretation of Shelley's role of the poet. In his final collection of poems, 1978's Primitive, Oppen again turns to Shelley, in the poem "Disasters," a poem that describes Oppen's visit to Israel in 1975:
of wars o western
wind and storm
of politics I am sick with a poet's
of the unacknowledged
world . . . (NCP, 267)
By referring to "Ode to the West Wind," Shelley's political poem calling for social reform, along with Shelley's description, in "A Defence of Poetry" of poets being the "legislators of the unacknowledged world," Oppen recognizes that Shelley's proclamation in relationship to the volatile political situation of Israel (the massacre of athletes at the Summer Olympics had occurred in 1972, the attack by Egypt and Syria in 1973) is hopelessly naive and idealistic. As Norman Finkelstein observes, "the historical conditions under which a poet writes have changed drastically"  since Shelley's time. No longer is the poet equated with the prophet, as he or she had been in the nineteenth century, a specifically Romantic interpretation, developed by that extended from William Blake to Walt Whitman to Allen Ginsberg, three poets Oppen particularly respected. Whitman, in particular, embodied this Shelleyan impulse in poetry, promoting the idea of the permanency of poetry and its role as progenitor of the sciences on which civilization is based. The poet, according to Whitman, is a kind of prognosticator: "he places himself where the future becomes present."  More interestingly, the poet, Whitman declares, "does not moralize or make applications of morals . . . he knows the soul."  Oppen, too, while accepting the idea of a specific kind of poetry, addressing those matters which might be of concern to an ostensible "future" and being heard ("it is even possible that it might be useful for the country to listen, to hear evidence, to consider what indeed we have brought forth on this continent" (SP, 179)) rejected the strictly moral implications of Shelley's "Defence," seeing poetry as something by which a "new vision" could be achieved, a place of questioning and creation rather than a clearinghouse for pre-established ideas or rhetorical clichés (SP, 174). These "completed" political moralities, after all, were the result of a metaphysical tradition of which the Heideggerean Oppen was attempting to reappraise through perception unburdened by "conceptions of right and wrong." Values, Oppen asserts in his essay, cannot be established by "ambition nor solidarity nor altruism," they can only be arrived at when "with whatever difficulty, with whatever sense of vertigo, we begin to speak for ourselves" (SP, 180).
Today, the poet remains outside the complex realm of public influence. By the end of the twentieth century, few were convinced that any modern poet had the political or philosophical influence previously enjoyed by poets. Indeed, since Shelley's time, there have been rare examples of poets directly engaged, through their art, in the public sphere in any substantial sense. The "world itself," Finkelstein continues, "is no longer acknowledged; poets legislate a value system whose existence is no longer even suspected; and the mode of discourse of which Shelley was to speak is no more . . . it is no wonder that Oppen feels a stranger to Shelley's visionary wind, which, while still rising like 'a gift / in the disorder,' cannot speak through the poet with its former resonance and rhetorical power." 
Another of Oppen's poems, "Ozymandias," serves as a critique of contemporary poetry. Just as "Disasters" makes use of Shelley's "Ode to the Western Wind" and his "Defence," Oppen's poem "Ozymandias" makes use of Shelley's sonnet of the same name, a poem that addresses human arrogance, the transience of power, emotional truth and the relationship of subject and artist. The themes of Oppen's poem are quite similar to Shelley's, though Oppen's approach is understated with considerably less grandiosity than his predecessor. Ozymandias himself is believed to be a reference to Ramesses the Great, a pharaoh of the nineteenth dynasty of Egypt, and Shelley's sonnet paraphrases the inscription of the base of this statue of Ramesses, "King of Kings am I, Ozymandias. If anyone would know how great I am and where I lie, let him surpass one of my works." In Shelley's poem, inspired by the arrival of the Egyptian colossus Ramesses II (pictured below), the lines read: "'My name is Ozymandias, king of kings: / Look on my works, ye mighty, and despair!" The statement is an admittedly extreme example of artistic hubris, of the artist's lack of humility, of competition with other artists, of vanity, pride, all of which, Oppen argues, are rather poor reasons for producing art.
To the one sense,
The sense of prominence,
Produce an art
And down town
The absurd stone trimming of the building tops
Rectangular in dawn, the shopper's
Thin morning monument (NCP, 59)
To achieve this "sense of prominence" as Ozymandias has, one must lose their other "five / Senses," one must become willingly blind, deaf, and dumb to a world that consistently undermines Ozymandias' claim. The absurdity of this claim is compared to the "absurd stone trimming of the building tops," absurd because, though like Shelley's "vast and trunkless legs of stone" that bear Ozymandias' words, the stone trimmings pretend importance, only to be ignored by those "shopper[s]" who would judge the stone's importance because it can neither be seen nor appreciated from their visual disadvantage from the street, placed so far below the "building tops." And, anyway, the shoppers are too busy purchasing their baubles to care. Therefore, the building tops, "Rectangular in dawn" are nothing more than "the shopper's / Thin morning monument." The artist, elevated far above those whom he or she means to address, alienates his or herself from anything other than his or her self-worth. Oppen's poem becomes a metaphor for those many poets that write from vanity in general, and one cannot help but assume that the poem is a metaphor for Ezra Pound, that most hubristic of modern poets.
Oppen's essay "The Mind's Own Place," in fact, was written in reaction to the rather dimsally didactic anti-Vietnam poetry of the less hubristic poet and friend Denise Levertov. While Shelley had argued for the moral quality of the imagination acting through poetry for man's regeneration, he insisted that its means should be indirect; the poem should instruct through delight. Shelley warns against the poet's embodiment of his or her "own conceptions of right and wrong, which are ususally those of his own place and time," as Levertov has done in her overtly political poems and which Oppen refused to do throughout his career as poet, most pointedly when in 1934 he stopped writing poetry rather than write proletariat verse. "By this assumption of the interior office of intepreting the effect of his or her political beliefs," the poet, Shelley argues, "would resign a glory in participation of the cause."  As Oppen observes in his essay, echoing Shelley, the "poet's business is not to use verse as an advanced form of rhetoric, nor to seek to give to political statements the aura of eternal truth. . . Therefore the poet speaking as a poet declares his political non-availability" (SP, 182). The poem cannot aeshetically survive such political advocacy. Shelley's introduction to Promethus Unbound states that "Didactic poetry is my abbhorrence; nothing can be equally well expressed in prose that is not tedious and supererogatory in verse."  Oppen, again echoing Shelley maintains that because the poem is a "test of truth" therefore "It is possible to say anything in abstract prose, but a great many things one believes or would like to believe or thinks he believes will not substantiate themselves in the concreete materials of the poem. It is not to say that the poet is immune to the 'real' world to say that he is not likely to find the moment, the image, in which a political generalization or any other generalization will prove its truth" (SP, 176). Elsewhere, Oppen could not consionably write "any statement already determined before the verse." The meaning of the poem begins "with the perception" (SL, 22). The point is to write one's perception, not to argue one's beliefs.
If the poet, Oppen observes, "ceases to believe in the validity of his insights – the truth of what he is saying, he become the casualty" of "the Bohemia that churns and worries the idea of the poet not-of-this-world, the disassociated poet," whose work loses its validity by having lost the "rare poetic quality of truthfulness." Modern American poetry, through its "skill of accuracy, of precision" and its "determination to find the image, the thing encountered, the thing seen each day . . . meant to replace by the data of experience the accepted poetry of their time," a poetry consisting of "a rhetoric of exaggeration, of inflation . . . a display by the poets of right thinking and right sentiment, a dreary waste of lies" (SP, 173-5). These poets had not followed Shelley's advice of "avoiding the [poetic, philosophical, political] conceptions of right and wrong in his own place and time" (emphasis mine). Thus, the title of Oppen's essay implies the specifically historical world in which the poet exists and with which he or she is in relationship, as opposed to the intellectual solipsism of Milton's Satan. The title may also refer to the Blakean interpretation of the passage in his The Marriage of Heaven and Hell, where the Devil, embodying Desire, was cast out by God, embodying reason, and "formed a heaven of what he stole from the Abyss." In his "Defence," Shelley interprets this as a moral victory, where
Nothing can exceed the energy and magnificence of Satan as expressed in Paradise Lost . . . Milton's Devil as a moral being is as far superior to his God, as one who perseveres in some purpose which he has conceived to be excellent in spite of adversity and torture, is to one who in the cold security of adversity and torture, is to one who in the cold security of undoubted triumph inflicts the most horrible revenge upon his enemy, not from any mistaken notion of inducing him to repent of any perseverance in enmity, but with the alleged design of exasperating him to deserve new torments.
Blake's interpretation is that Satan represents Desire, or more loosely translated, emotion, the active energy which resists the stasis of reason, the poet, according to Blake, is of the "Devil's party."  As Harold Bloom observes,
like Blake, [Shelley] makes a comparison between energy or desire, on the one side, and the restrainer or energy or desire, on the other. Like Blake's, his real point is that Paradise Lost has not and cannot have any hero. Its only possible hero, the embodiment of human energy and desire at their highest pitch of imaginative intensity, its Orc or Prometheus is Satan. He is made to accept the same categories of morality as God by being portrayed as a being who lives, or tries to live, by a frank and simple inversion of the conventional theological and moral categories. 
As Bloom also observes, Shelley saw something of Prometheus in Satan. In his introduction to Prometheus Unbound, Shelley writes
The only imaginary being resembling in any degree Prometheus, is Satan, and Prometheus is, in my judgment, a more poetical character than Satan because, in addition to courage and majesty and firm and patient opposition to omnipotent force, he is susceptible of being described as exempt from the taints of ambition, envy , revenge, and a desire for personal aggrandisement, which, in the Hero of Paradise Lost, interfere with the interest. The character of Satan engenders in the mind a pernicious casuistry which leads us to weigh his faults with his wrongs, and to excuse the former because the latter exceed all measure. In the minds of those who consider that magnificent fiction with a religious feeling, it engenders something worse. But Prometheus is, as it were, the type of the highest perfection of moral and intellectual nature, impelled by the purest and truest motives to be best and noblest ends. 
If Satan and Prometheus represent for Blake and for Shelley the possilibility of acting against the chains of reason "impelled by the purest and truest motives" and creatively establishing a "universal regeneration by an apocalypse of the moral imagination," then Shelley's use of the image the Amphisbaena, a mythic serpent with a head at each end of its body, serves as a reminder that what is required in order to maintain this "restoration of moral and political order . . . is an unremitting vigilance lest the serpant deep in human nature should break loose and start the cycle [of humanity's fall] all over again." 
Shelley's use of this mythic serpent resonates with Oppen's use in "A Narrative," a poem that repeats a number of images and arguments from Oppen's essay, the serpent Ouroborous, the self-consuming serpent at the center of the world, equated with the "devil's / Doctrine the blind man / Knew. His mind / Is its own place" (NCP, 153). Yet where Oppen's Ouroboros represents the metaphysical and moral categories of which blind us to our open perception of the world, in Shelley's poem Amphisbaena represents an historical fatalism that Oppen's "Narrative," with its concluding encounter with "Permancence" in the "open / Miracle / Of place" (the mind's own place) ultimately rejects (NCP, 156).  Where Shelley's serpent
resonates more is Oppen's "Leviathan," the mythical creature that threatens to overtake us from fear and a reticence to discuss the difficulties of our historical circumstances and its immediate metaphysical and moral implications.
Finally, the title of Oppen's essay points to the dishonesties of political convictions that, in Oppen's words, "will not substantiate themselves in the concrete materials of the poem" (SP, 176). "I am the father of no country / And can lie" Oppen writes in "A Narrative," asserting that because he does not pretend to be in possession of politcal truths, he can move beyond the "right thinking and right sentiment," the very transgression for which the poets as "liars" were to be removed from Plato's Republic. "But whether mendancity," Oppen wonders, "Is really the best policy. And whether / One is not afraid / To lie" (NCP, 150). One must rise above the "terrible thin scratching of the art world" by describing more than "everything that we already know," and declaring "every belief that we already hold," or discussing more than "those things we are accustomed to talk about, unless we somehow restore meaning to a word" (SP, 174-5). The mind's own place is the world, a world that constantly presents the poet with images and ideas which either refute or support our beliefs. The poem as an "act of perception," laid open to these images and ideas, is then the location in which these beliefs are tested.
The "terrible thin scratching" of the art world, the "art of the massuer" and the "perfumist," the art of "soft lights" and "background music" are qualities evoked in "A Narrative": "The constant signing / Of the radios and the art // Of colored lights / And the perfumist / Also are art" (NCP, 150). Oppen associates these forms of art with the term "Beauty," a term that Shelley touted in his essay as an integral aspect of poetry, which "turns all things to loveliness . . . exalting the beauty of that which is most beautiful . . . adding beauty to that which is most deformed."  Yet Oppen cannot accept this "Beauty" which acts as a "cocoon" for the "emotion which creates art . . . the emotion which seeks to know and disclose" (SP, 173). "Art can move forward," he explains, "only when some man, or some men, get their head above – or below – the terrible thin scratching of the art world . . . It is possible to find a metaphor for anything, an analogue: but the image is encountered and not found" (SP, 175). What is required of the poet is "a new vision" (SP, 174). Poetry is not found in the perfumist or the masseur, but in the harsh objects of "daylight / / In which things explain each other, / Not themselves" (NCP, 151).
Shelley speaks of the "savage" who "expresses the emotions produced in him by surrounding objects" ("there are things we live among," Oppen writes, "'and to see them / Is to know ourselves"' (NCP, 163)), much as the "child at play by itself will express its delight by its voice and motions; and every inflexion of tone and every gesture will bear exact relation to a corresponding antitype in the pleasure impressions which have awakened it." This imitation of natural objects exists in all men, Shelley explains, but those to "whom it exists in excess are poets, in the most universal sense of the word; and the pleasure resulting from the manner in which they express the influence of society or nature upon their own minds, communicates itself to others, and gathers a sort of reduplication from that community." Thus the poet restores that primitive emotional force that existed "in the youth of the world."  This poetic quality, possessed by Blake, Whitman, and Oppen, involves what Denis Saurat describes as a "gregarious sense." These poets are "intensely conscious of the group, the nation, and beyond that, the earth itself, and of their kinship with all beings, with nature, with the Cosmos . . . their power of intuition and expression; all qualities which make a primitive of the poet." 
What interested Oppen more was Shelley's concept of the poet's role of creating a "being within our being." The poet, as the Heideggerean care-taker of language and being, enacts a return to the primitive, originary energies of language and there by address the condition of our being, to find in words their luminous, pristine meaning and to awaken through "unapprehended inspiration" a world "to which the familiar world is chaos" (NCP, 116). The poet's vocation, Oppen argues, is therefore "legislator of the unacknowledged world" [emphasis mine] (NCP, 286), the world in which poetry makes us inhabitants, the "being within our being."