Depending on your tolerance for the existential anguish that defines so many of Woody Allen’s characters, a philosophy professor is either the perfect protagonist for one of his movies, or the worst. In the director’s new film Irrational Man (out July 17), Joaquin Phoenix is the latest actor to take the lead, with Allen now outsourcing roles he once played himself to younger actors carrying out onscreen affairs with actresses even younger still (in this case, it’s Emma Stone).

Phoenix’s Abe Lucas is a reputed but heavy-drinking philosophy professor whose morose detachment elicits lust—both intellectual and sexual—from faculty and students alike. After a series of personal misfortunes and a few too many nights wrestling with long-dead existentialists, he has come to possess what his student Jill (Stone) describes as a “bleak view of existence.” He’s also come to seriously question whether his chosen discipline isn’t merely “verbal masturbation,” a “theoretical world of bulls–t” that’s no match for the trials of real life.

As Abe navigates his feelings for Jill, the advances of his colleague Rita Richards (Parker Posey) and a disturbing plan to inject purpose into his meaningless existence—by murdering a perfect stranger to improve the life of another stranger—hardly ten minutes pass without hearing him name-drop a philosopher. Though Philosophy 101 isn’t a prerequisite for the film, a refresher on the thinkers whose theories connect the plot’s dots will keep audiences in step with Abe’s evolving existential circumstances.

Immanuel Kant: None of these philosophers can be summarized in a tidy paragraph—least of all Kant—but of all the 18th century philosopher’s work on metaphysics, epistemology, ethics and aesthetics, his notion of a categorical imperative is the one referenced most frequently in Irrational Man. The concept on morality and reason, introduced in 1785, states that one must “Act only according to that maxim by which you can, at the same time, will that it should become a universal law.” Practically speaking, the moral thing to do in a situation is the action that would be universally moral no matter the circumstances. The action’s consequences are inconsequential, because the morality exists in the act itself.

The categorical imperative also suggests that one can never lie to another person, for any reason, even if the asker is a murderer seeking information to help carry out a killing. Abe chooses to ignore the categorical imperative, making a decision the morality of which is explicitly wrapped up in the specifics of the circumstance—one which, if universalized, would spell disaster. Allen, for his part, told the New York Times he believes the concept to be limited: “The problem with the categorical imperative is that you always try to use it in these trivial life decisions… The truth is there are decisions you make in life where you can’t go by it, it’s not a reliable thing.”

Søren Kierkegaard: Often considered the father of existentialism, Kierkegaard, like Allen, was rather preoccupied with death—possibly because his parents and all but one of his siblings died by the time he was in his mid-twenties. He is attributed with the term “angst,” a human condition linked to the terror that results from our freedom of choice. In facing this “dizziness of freedom,” he believed, humans are overwhelmed by possibilities—to jump or not to jump, for instance—but we also reach a deeper self-awareness.

Abe references Kierkegaard’s The Sickness Unto Death, which the philosopher wrote under the pseudonym Anti-Climacus in 1849. For the Christian existentialist Kierkegaard, this sickness was, in a word, despair, which he believed resulted from failing to align with God’s plan for oneself. Phoenix’s Abe is certainly characterized by some kind of despair—but his antidote, rather than seeking out a god, is to play one himself.

Martin Heidegger: That Abe references Heidegger with derision, in the same breath as “fascism,” isn’t surprising given the German philosopher’s affiliation with the Nazi Party. Though he made significant contributions in the realms of existentialism, political theory, hermeneutics and other fields, his anti-Semitic writings have come to contaminate his reputation.

Abe’s equation of Heidegger with fascism, in a breezy aside, is a bit of an oversimplification. Heidegger was concerned with what it means to be, as he explored in his seminal 1927 work, Being and Time. While fascism presupposes a dictator ruling over a faceless crowd, Heidegger’s thoughts on being encourage accepting the inevitability of death as motivation to live for oneself, and acknowledging other people as ends rather than means. Still, Heidegger’s adherents today grapple with the cloud that hangs over his career.

Jean-Paul Sartre: A key 20th century figure in existentialism, phenomenology and Marxism, Sartre wrote that we are “condemned to be free.” Free will exists, he believed, and humans must acknowledge that freedom and make meaning of our existence as we go along, for meaning does not exist just because we exist. We must not live in accordance with a set of preordained meanings (capitalism, for example), for to do so falsely removes the burden of our own freedom.

Abe quotes Sartre as having said that “hell is other people,” which is, in a way, a misquote, or at least an oft-misinterpreted line. It comes from a 1944 play by Sartre, “No Exit” (Sartre, therefore, penned but did not himself utter the words), and is often misinterpreted to mean exactly what it implies. Sartre said that what he actually meant is that our own self-judgment is colored by how we perceive others to judge us. Abe seems immune to such a notion, as he justifies his actions without regard for the potential judgment of others.

Hannah Arendt: It bears mentioning that Arendt, though often labeled a philosopher, described herself as a political theorist, as she dealt with men (and women) in the plural, as opposed to “man,” singular. She wrote on many subjects, from totalitarianism to revolution to the nature of freedom, but one of her best known works is Eichmann in Jerusalem: A Report on the Banality of Evil (1963), and this reverberating catchphrase— “the banality of evil” —is the concept invoked by Allen in Irrational Man.

The phrase describes a phenomenon Arendt observed in Adolf Eichmann and other Nazis who claimed that in carrying out the Holocaust, they were simply following orders and doing their jobs, which in their views abdicated them of responsibility. Arendt wrote that even under a totalitarian regime, moral choice remains. Eichmann, rather than acting on evil impulses, acted in an unthinking manner: a bureaucrat incapable of comprehending the consequences of his actions on his victims. As far as the banality of evil plays out in Abe’s world, his decision to do evil does not originate from outside of himself, nor is he a cog in the regime—he just chooses to create his own framework of morality and evil.

Simone de Beauvoir: Though she produced work on a wide array of subjects, de Beauvoir’s most influential writing is The Second Sex, a 1949 treatise on the oppression of women, which is often credited with inspiring second-wave feminism. In the book, de Beauvoir traces the position of women through the perspectives of biology, psychology, social structures, history, religion and politics, concluding, among other things, that “it is not women’s inferiority that has determined their historical insignificance: it is their historical insignificance that has doomed them to inferiority.”

Abe and Jill can both quote de Beauvoir from memory, though the way Jill’s character is written—her whole world revolves around her infatuation with her professor—shows she’s not exactly a living embodiment of the philosopher’s ideas. De Beauvoir’s writings on ethics, and the responsibility of individual human beings to their fellow humans, are actually much more relevant to the themes explored in Irrational Man.

As to the feminism of Allen’s works, that’s a topic for another day.

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Write to Eliza Berman at eliza.berman@time.com.