Woody Allen, apparently, has something to confide. Year after year, movie after movie, he comes back to a select few themes and ideas over and over again. His latest film, “Irrational Man,” returns to a question he has circled in “Crimes and Misdemeanors,” “Match Point” and “Cassandra’s Dream” — namely, what can you get away with and still go on living with yourself? Is there any act so unspeakable that it forever changes a person?

The new movie remains tonally elusive, changing at times scene by scene or even moment by moment between playful comedy and something more downcast and ruminative. Allen’s new “Man” isn’t so much irrational as stubbornly, willfully weird.

“IRRATIONAL MAN” Rated: R Opens Friday at Dole Cannery Stadium 18 and Kahala 8

Joaquin Phoenix plays Abe Lucas, a self-styled bad-boy philosophy professor who has arrived at a small campus to teach for a summer. Abe, depressed and usually drunk, still manages to become an immediate big man on campus, capturing the attention of Jill Pollard (Emma Stone), an impressionable young student, and Rita Richards (Parker Posey), a science professor feeling trapped in her job and marriage. Their affections seem lost on Abe, adrift in his own malaise, and it is only once he turns to something more sinister that he is able to revive himself.

The film plays out as a light satire of campus manners airlessly trapped within a bell jar of dour seriousness — what Allen in “Annie Hall” once called “heaviosity.” The film is peppered with references to various greatest hits of the liberal arts canon, Kant and Kierkegaard, Dostoyevsky and De Beauvoir, elevating the cloistered, hermetic atmosphere. The dark mood threatens to become a parody of itself until Allen punctures his own pretenses with a laugh line like, “Just what the world needs, another book about Heidegger and fascism.”

As Allen moves relentlessly, restlessly from movie to movie, he creates each one in self-imposed secrecy, so as a film such as “Irrational Man” is first unveiled, audiences usually have no real idea of whether it is a lightweight, purposefully inessential comedy such as last year’s “Magic in the Moonlight” or something of a more piercing nature like the previous year’s “Blue Jasmine.”

This time Allen, who turns 80 later this year, seems fully aware that the scraps of information audiences may know — mainly Phoenix and Stone in a teacher-student affair — are a bit of misdirection. Allen may read his press after all, teasing at the connections anyone looking to get upset by another age-imbalanced on-screen romance will make to his own off-screen life, long a source of simmering, and recently renewed, controversy. As Abe splits his time between Jill and Rita, and as scenes move from one to the other, a viewer may be rooting for Rita to be the one at Abe’s side and let down when she is not.

In early scenes, Phoenix’s potbelly essentially precedes him on the screen, and his boozy blankness when he first meets the college dean is a thing of understated comic, awkward wonder, timed just behind the beat. As the story moves along and his somnambulant stupor turns to confident excitement and then mania, Phoenix manages the rare feat of playing the male lead in a Woody Allen film without aping the well-known manner of Woody Allen.

Coming after Phoenix’s astonishing recent run of physically transformative, emotionally explosive performances, including “The Master,” “Her,” “The Immigrant” and “Inherent Vice,” it is likely this will be dismissed as a lesser turn. Yet no one conveys inner torment quite like he does, and today any role Phoenix takes on makes for necessary viewing, as he is the most exciting American actor working today.

The idea of Parker Posey in a Woody Allen movie brings to mind a certain loose, fast-talking urbane type, and it is to the credit of both of them that here she is not that. Rather, she gives a moody, wise performance that underscores just how underserved Posey has been by Hollywood and even its indie outliers. Her performance is steely rather than brassy, tinged with sadness, desperation and resignation, and hopefully sparks a new run of mature, resonant roles.

“Irrational Man” will likely change no one’s mind about what to do with Woody Allen.

There will undoubtedly be those who will comb this film for signals or confessions, tells or traces of something more. Down to the 1960s soul jazz of the Ramsey Lewis Trio featured on the soundtrack, in its own strange, deliberate way the film does wind up feeling surprising, fresh even, as Allen finds new ways to explore some of his most long-standing preoccupations.

The film’s most unexpected wallop, right at the end, is a deeply felt consideration not only of how decisions and actions alter the main character of Abe but also his unintended collateral victims and what they are forced to live with after. “Irrational Man” never does make sense of the inscrutable Abe, just as most people, Allen included, remain mysteries to themselves and others. This finally reveals the film to be neither comedy nor drama, but an all too human horror story where the monster is within.

Review by Mark Olsen, Los Angeles Times