How Do You Know

“How Do You Know” is only the start of the question. The rest of it is “… when you’re in love, and when the person you’re in love with is right for you?” Which, if you think about it, is the same question asked by every romantic comedy, not just this one. The answer is something like, “Well, first you stay with the wrong guy for a while even though it’s obviously wrong, while taking for granted the nicer, better option who keeps presenting himself to you, and then eventually you wise up.” It’s not exactly rocket science.

Indeed, “How Do You Know” doesn’t cover any new territory. Writer-director James L. Brooks (“Broadcast News,” “As Good As It Gets”) isn’t interested in subverting cliches or surprising his audience. He set out to make the sort of urbane rom-com that mildly upscale couples would go to see — something wittier than Nora Ephron but less cosmopolitan than Woody Allen. The result isn’t anything special, but Brooks did make the very wise decision to cast Paul Rudd and Reese Witherspoon in the lead roles.

I didn’t realize it had been two years since Witherspoon had appeared onscreen until Entertainment Weekly told me, but “How Do You Know” makes me realize I’ve missed her. As Lisa, a professional softball player recently cut from her team, Witherspoon draws on her twin strengths of pluckiness and determination, mixed with some cuteness (but not cutesy-ness) as Lisa tries to make the most of her new situation. Lisa is known among her associates as a pillar of strength, a make-lemonade-out-of-them-lemons kind of gal. She has multiple affirmations taped to her mirror, including this one: “Courage is mastery of fear, not absence of fear.”

Lisa has been casually dating Matty (Owen Wilson), a pitcher for the Washington Nationals who is defined by his promiscuity, carefree behavior, and good-natured insensitivity. He’s an idiot, but he’s the kind of idiot who will be just right for some girl. That girl is clearly not Lisa, however.

Meanwhile, there is George (Rudd), a thoroughly nice guy who works in high finance and is entirely too nice to be working in high finance. As a result of this, he has come under investigation by the Justice Department for stock fraud. He’s baffled by the allegations, certain that if he did anything wrong it was an honest mistake. Still, the company must distance itself from him, even though his father (Jack Nicholson) is the owner.

And so George and Lisa meet when both of their lives are in the process of changing dramatically. They’re unemployed now, though don’t think for a second that “How Do You Know” will address anything as distasteful as money problems. Instead, we’re treated to an amusing dissection of the ways people cope. Lisa is determined not to let her emotions get the best of her. George, dazed by the setbacks, remains optimistic and is eager to let Lisa be a ray of sunshine. She’s too independent and he’s too vulnerable, but they’re both insanely likable. How is it that nearly everything Paul Rudd does, here and elsewhere, is so utterly delightful?

On paper, much of this doesn’t work. There’s a scene where George’s former secretary, Annie (Kathryn Hahn), and her long-term non-committal boyfriend have a breakthrough, which is witnessed by George and Lisa, who take lessons of their own from it. The set-up couldn’t be more obvious, yet it comes across as sweet, not calculated. In another sequence, Lisa has a fight with Matty and winds up hanging out at George’s apartment. In the context of the story, it’s wholly implausible: she barely knows George, he lives outside the city, and so forth. And yet this turned out to be one of my favorite scenes because of Rudd and Witherspoon’s sparkling interaction.

Last week “The Tourist” reminded us that even the biggest stars can’t always elevate mediocre material. “How Do You Know” is an instance where it works. It’s glossy and entirely forgettable, but the friendly, funny cast makes it worth seeing.

B- (1 hr., 56 min.; PG-13, one scene with three F-words, some brief mild sexuality.)