Emma Stone, ever charming and versatile, is great as Jill Pollard, a student at an East Coast college named Braylin. She has a boyfriend but falls in love with her philosophy professor, Abe Lucas, who arrives at Braylin to teach a summer course after stirring controversy with his unorthodox ideas and a reputation for being a womanizer. He also carries a flask, from which he imbibes frequently, even as he walks along the campus. Abe is depressed and laments that nothing is worthwhile. However, he has charm and a super intellect, and Jill becomes infatuated as their friendship progresses, even though he tries to hold her off.

Joaquin Phoenix is a perfect choice as Abe, effectively conveying Abe’s complexity and steadily building toward more outrageous moments as the plot develops.

A special revelation in the film is Parker Posey as Rita Richards, a faculty member who is unhappily married and comes on strong to Abe. She is very emotionally needy and it is clear that if he would run off with her to Spain, as she fantasizes, she would be ultra devoted to him. Even when the film’s major question of Abe’s morality arises, Rita has a great line indicating that it wouldn’t matter. Such is her passion for him.

Posey has long been known for her effectiveness in various indie roles, and here she further shows her skills to give a profound, feeling and affecting performance, a very mature one that is a highlight of the film.

Jamie Blackley does well in his role as Roy, Jill’s college boyfriend who expects to marry her, is jealous of what he sees as her developing relationship with Abe and has to swallow his pride and come to grips with Jill’s veering path.

The plot that deepens the film is built upon Abe’s feeling that despite all of the philosophy he expounds upon in the classroom, marked by his effort at debunking conventional thinking, he feels terribly frustrated at the state of the world and his perceived inability to make a difference. He regards himself as having slumped into a life of inaction, which affects his sexual capability and overall motivation.

But one day while he and Jill are dining, they overhear a conversation in the booth behind them in which a mother is lamenting how a biased judge has stacked the cards against her in her desperate fight for custody of her children. It sparks in Abe a wonder of what would happen if at last he gave his life some meaning by taking action against that judge to help the beleaguered mother. Morality or immorality? Rationality or irrationality? Allen’s fascination with philosophy fuels his screenplay and in very in concrete ways.

As Abe’s outlook on life perks up with his plans to do what to him would be a meaningful act, there is a build-up of suspense, in large measure due to Allen’s writing and direction, but also in great measure to the superb performances he gets from his cast. There also are few filmic touches that will remind buffs of Hitchcock ploys.

(The philosophical questions posed in the film can stimulate thought about issues faced throughout history and produce endless discussion and speculation. What if someone feeling the need to act would have succeeded in assassinating Hitler? A good or immoral deed for the world? Assassinations can bring vast changes. Back in the 1950s, for example. what if someone with feelings like the those of Abe targeting an unfair judge in “Irrational Man” had knocked off biased judge Irving Kaufman, who in the hysteria of the times with his obvious desire to ingratiate himself sentenced Ethel and Julius Rosenberg to death in the still-famous case? Would a more objective judge have done that? In a different global-reaching vein, what if John F. Kennedy had NOT been assassinated, how would that have changed history? One could go on and on with what ifs.)