Socrates, the fifth-century BCE Athenian philosopher, serves as a central figure in Twilight of the Idols. Nietzsche portrays him as a case study in cultural decay, using him to develop a broader critique of rationalism, morality, and Western philosophy. Nietzsche begins with what he presents as a physiological diagnosis, arguing that Socrates’s plebeian background and reputed ugliness reflected what he regards as a disordered, decadent nature. For Nietzsche, Socrates’s inner life was a “cave of bad appetites” (11), and his philosophical project was what Nietzsche portrays as an extreme, life-denying attempt designed to control his own chaotic instincts. Nietzsche therefore interprets Socratic philosophy less as a search for truth than as an effort to impose rational control over instincts that he believed Socrates feared.

For Nietzsche, Socrates represents a pivotal turning point in Greek culture. He was the figure who championed dialectic—logical argument—over the noble, instinctual taste of the older Hellenes. This shift, according to Nietzsche, marks the moment when “with dialectics the plebs c[a]me to the top” (9). Socrates’s famous equation, “Reason equals virtue and happiness” (11), is to Nietzsche a “most bizarre” formula, born not of strength but of what Nietzsche sees as a desperate need to impose order on inner anarchy. Nietzsche argues that Socrates treated rational self-control as the path to virtue because he believed that reason could master conflicting instincts. By making reason the governing principle over the instincts, Nietzsche argues that Socrates initiated a tradition that devalues the body, the senses, and life itself.

Nietzsche interprets Socrates’s method of dialectic as a tool of revenge. He argues that Socrates’s lower social status shaped his reliance on argumentative reasoning as a weapon to humiliate and dominate the noble Athenians he engaged. The dialectician, Nietzsche claims, renders their opponent powerless, forcing them to prove that they aren’t an “idiot.” For Nietzsche, dialectic is a technique used by those he believes lack other, more noble forms of power, expressing the ressentiment of the weak.

Ultimately, Socrates functions as Nietzsche’s primary example in his broader argument against rationalism as a cure for cultural decline. Nietzsche argues that the Socratic cure is simply another form of the disease. He concludes that “to have to fight the instincts—that is the definition of decadence: as long as life is ascending, happiness equals instinct” (12). Socrates’s faith in “rationality at any price” was a misunderstanding of both health and virtue (12), making him a symbol of the anti-natural morality that Nietzsche seeks to overcome.

Plato, the fifth-century BCE Athenian philosopher and founder of the Academy, is, for Nietzsche, the primary architect of the great error that has poisoned Western thought: the invention of a metaphysical “true world.” As Socrates’s student, Plato systematized his teacher’s rationalism into a comprehensive philosophical system that fundamentally split reality into two realms. Nietzsche targets him as the thinker most responsible for what Nietzsche sees as devaluing the physical, sensory world of becoming in favor of a fictional, eternal world of being.

For Nietzsche, Plato’s key innovation, the theory of forms, epitomizes the philosophical tendency that Nietzsche critiques as life denying. By positing a higher, eternal reality of perfect forms accessible only through reason, Plato reframes the empirical world as a mere shadow or simulacrum of a “real” world inaccessible to the senses.

Immanuel Kant, the 18th-century German philosopher, stands as a central figure in Nietzsche’s critique of modern thought. Nietzsche identifies him as the most sophisticated—and therefore most insidious—heir to the Platonic-Christian metaphysical tradition. Though Kant’s project was framed in the secular language of the Enlightenment, Nietzsche diagnoses it as a continuation of the same life-denying impulse, calling Kant an “underhanded Christian.” For Nietzsche, his philosophy represents the culmination of the error of inventing a “true world” beyond the senses.

Nietzsche argues that Kant’s distinction between the phenomenal world (the world of appearances) and the noumenal world (the unknowable “thing-in-itself” [30]) is merely a modern, more skeptical version of Plato’s two-world system. By making the true world indemonstrable yet an object of moral faith, Kant perpetuated the core metaphysical slander against reality. Nietzsche sees Kant’s moral philosophy, based on the “categorical imperative,” as a secularized command theology, an attempt to preserve Christian moral authority after the death of God.

Moreover, Nietzsche critiques Kant’s methodology, arguing that he mistakes the structures of human grammar and psychology for universal laws of reason. The belief that concepts like causality or the self originate in a higher, non-empirical realm is, for Nietzsche, a symptom of philosophical vanity. He asserts that this error arises from a mistaken premise: “[W]e must have been divine, because we have reason!” (17). This perspective fails to recognize that our categories of thought are contingent and human, not divine.

In Nietzsche’s historical narrative of error, Kant represents the pale, “Königsbergian” phase where the idea of the true world becomes subtle, elusive, and obligatory but no longer truly believed. By confronting Kant directly, Nietzsche seeks to dismantle what he regards as one of the last major expressions of metaphysical philosophy and redirect philosophy toward affirming the only world he believes exists: the world of appearance, becoming, and life.

Arthur Schopenhauer, the 19th-century German philosopher of pessimism, is one of Nietzsche’s most significant intellectual adversaries. Having once been an admirer, Nietzsche came to see Schopenhauer’s philosophy as the ultimate expression of a decadent, life-negating worldview. Schopenhauer’s central thesis—that existence is driven by an oblivious, irrational, and insatiable “Will” that inevitably causes suffering—leads him to conclude that the highest ethical goal is the denial of this will to life. Nietzsche presents his own philosophy of life affirmation as a direct response.

Nietzsche rejects Schopenhauer’s interpretation of art, genius, and tragedy. Where Schopenhauer sees these phenomena as momentary respites from the torment of the Will—a temporary “redemption”—Nietzsche sees them as expressions of an overflowing will to power. For Schopenhauer, tragedy teaches resignation; for Nietzsche, it’s a tonic for the strong, a celebration of life that affirms even its most terrible and destructive aspects. He accuses Schopenhauer of performing the “greatest psychological counterfeit in all history, not counting Christianity” (64), by reinterpreting humanity’s greatest moments of self-affirmation as evidence for a nihilistic conclusion.

Central to this dispute is the valuation of pity. Schopenhauer places compassion at the core of morality, viewing it as the means by which one overcomes selfish individualism. Nietzsche, in contrast, argues that pity is a debilitating emotion that multiplies suffering and drains vitality. He subjects the morality of pity to genealogical critique, branding it a tool of the weak and a symptom of decadence. For Nietzsche, Schopenhauer’s system, in its elevation of pity and its ultimate goal of nothingness, is the modern philosophical articulation of the Christian “slave morality.”

Ultimately, Schopenhauer serves as the catalyst for Nietzsche’s revaluation project. By providing a modern, atheistic, and philosophically rigorous argument for life denial, Schopenhauer embodies the very perspective that Nietzsche must overcome. In refuting him, Nietzsche clarifies his own concepts of the Dionysian, the will to power, and a tragic pessimism that says “yes” to life instead of “no.”

Johann Wolfgang von Goethe, the 18th- and 19th-century German writer, statesman, and polymath, occupies a distinctive place in Twilight of the Idols as one of the few historical figures whom Nietzsche openly admires. Nietzsche presents Goethe as an example of psychological health and intellectual maturity, seeing in him a way of engaging with life that contrasts with the forms of decadence examined elsewhere in the text. Goethe's importance extends beyond his literary achievements because, for Nietzsche, his life and work embody a mode of existence grounded in growth, self-cultivation, and engagement with the world.

Nietzsche praises Goethe as a “strong, highly cultivated human being” whose character reflects the integration rather than the suppression of human instincts (52). Goethe does not seek moral or metaphysical escape from suffering. Instead, Nietzsche argues that he transforms experience into a source of creative and intellectual development. His appreciation of nature, his resistance to rigid moral systems, and his willingness to confront complexity without appealing to transcendent ideals exemplify the qualities that Nietzsche associates with strength rather than decadence.

Goethe also illustrates Nietzsche’s rejection of metaphysical philosophy. Nietzsche argues that Goethe remains committed to the world of experience instead of measuring reality against an imagined higher realm. This orientation reflects the same affirmation of becoming that underlies Nietzsche’s critique of Plato, Christianity, and Kant. Goethe therefore demonstrates that intellectual achievement need not depend on denying the value of the sensory world or subordinating life to abstract moral principles.

Heraclitus, the pre-Socratic philosopher from Ephesus, is one of the few thinkers for whom Nietzsche expresses consistent admiration. He stands as a key exception to Nietzsche’s general condemnation of philosophers, who he believes have historically falsified reality. Nietzsche praises Heraclitus for his courageous affirmation of a world of perpetual flux and becoming, a stark contrast to the static, eternal “Being” championed by the Eleatic school and later perfected by Plato.

Heraclitus’s philosophy provides crucial support for Nietzsche’s own anti-metaphysical project. By asserting that the senses do not lie when they show multiplicity and change, Heraclitus validates Nietzsche’s argument that the “apparent” world is the only world. He becomes an ancient ally in the fight against the philosophical separation of reality into a “true” world and an “apparent” one.

Thucydides, the fifth-century BCE Athenian historian and general, is celebrated by Nietzsche as a paragon of intellectual courage and realism. In the midst of what Nietzsche considers the “moralistic and idealistic swindle” of the Socratic schools (96), Thucydides stands out for his disciplined and unsentimental analysis of power, war, and human nature. For Nietzsche, he embodies the Sophistic culture he admires, which sought to understand the world without illusion.

Nietzsche presents Thucydides as the perfect antidote to Plato. While Plato fled from the harshness of reality into an idealized world of forms, Thucydides confronted it directly. Nietzsche praises his “unconditional will not to delude oneself, but to see reason in reality—not in ‘reason,’ still less in ‘morality’” (96). For Nietzsche, this commitment to factual reality reflects the strength of the older Greek instinct before it gave way to philosophical idealism. Thucydides exemplifies the self-mastery and clear-sightedness that Nietzsche believes are necessary to understand the world without the distortions of metaphysical and moral ideals.

Jean-Jacques Rousseau, the 18th-century Genevan philosopher, serves as one of Nietzsche’s primary targets in his critique of modernity. Nietzsche identifies him as the “first modern man, idealist and rabble in one person” (90), a figure whose sentimental moralism and revolutionary ideas embody the essence of decadence. Nietzsche criticizes Rousseau’s famous call for a “return to nature” (50), arguing that it idealizes what he regards as a non-existent state of natural virtue and uses that ideal to condemn civilization.

Nietzsche sees Rousseau’s philosophy as an expression of plebeian ressentiment. He traces the doctrine of equality, which he calls the “most poisonous poison anywhere” (90), to Rousseau’s influence. Nietzsche argues that appeals to equality made in the name of justice undermine what he regards as true justice, which requires treating unequal things unequally. He also links Rousseau’s thought to the French Revolution, which he describes as a “bloody farce” animated by a morality that, in Nietzsche’s view, elevates herd values and turns against aristocratic ideals.