“Maggie’s Plan” is a pleasant, intriguing film. Greta Gerwig stars as the Greta Gerwig we met in “Frances Ha.” But the other two actors, Ethan Hawke and Julianne Moore, play abstruse academics as successful writers. The film postulates that their characters are more intelligent than the Gerwig character. Moore with her Danish accent might be based on writer/director Rebecca Miller’s mother Inge Morath. Hawke might be said to resemble her father Arthur Miller. Who, ergo, is Greta Gerwig but–Marilyn Monroe? She’s no Greta Garbo. The film’s a screwball comedy that makes me speculate. And of course Miller is married to–Daniel Day-Lewis.