Sometimes you get the idea that the slogan of the American Medical Association is, "If it ain't broke, we fix it until it is." Doctors, with all their education and degrees--nay, because of their education and degrees--sometimes mess us up really good. Since so many of our ailments originate in our heads, or at least partially so, maybe we'd be better off being "treated" by a good friend or by any nice guy willing to listen carefully and comment graciously on their take. Ivan Reitman acquitted himself just fine six years ago with a similar concept, his "Dave," about an incapacitated president who is replaced by a lookalike phony, an ordinary, likeable fellow, who even hires a local accountant to take care of the federal budget. The country prospers.

"Mumford," like "Dave," is a godsend to those of us who believe that we could well strip away a good deal of jargon- filled fields and substitute good common sense for fancy diagnoses and treatments. Specifically relating to the profession of psychoanalysis, the movie directed by Lawrence Kasdan ("Body Heat") from his own script could have you leaving the theater feeling so good that the eight bucks you paid for admission could be a better value than the $200 you might pay to a shrink for two sessions on the couch. The story's amiability can be credited largely to the down-home performance of Loren Dean, in the role of a true Mr. Nice Guy All-American (despite his commission of a criminal act), who shrinks the heads of a number of people of his village. resolving age-old problems and bringing happiness and good cheer. Of course none of this is believable. Dean's character, Dr. Mumford himself, concedes at one point that psychologists can't do a heck of a lot for people whose problems originated in their early childhoods. Then again, maybe a good friend and not a professional head-doctor could do the job: and that's exactly what Mumford is--a phony, a quack, and a stroke of luck to the village in which he works.

Crosscutting in a conventional manner, sometimes jaggedly from one patient to another, "Mumford" establishes the tone of an outwardly friendly town whose residents are anything but dangerous but whose lodgers have difficulties they take to the doctor's couch. Sofie Crisp (Hope Davis) has been diagnosed with Epstein-Barr syndrome and is so regularly exhausted that she at first cannot even make the walk to the psychologist's office. Skip Skiperton (Jason Lee), as congenial a fellow as you want to meet, has made three billion dollars by cornering the market on the production of modems but cannot have a relationship with a woman because he is sure they are all after his money (and he's right). Althea Brockett (Mary McDonnell) is trapped in a loveless marriage with a wealthy industrialist (Ten Danson) who is a jerk and consoles herself with compulsive mail-order whopping while Henry Follett, the fat and balding local pharmacist, has perpetual fantasies that he is a sexy character in a noir movie being vamped by cleavage-rich femmes. One by one, Mumford finds a solution within months for each of these delightfully troubled people, but a discovery made by two envious psychologists (Jane Adams and David Paymer) with the help of the town's snotty lawyer (Martin Short) creates a predicament for Mumford and a loss for the entire town.

Mumford" is an oddity. Starting off with a blast of music and a black-and-white scene from a detective story that sets a tone of danger and tension, Kasdan settles into a phlegmatic style. The entire picture seems to lack energy-- whether a deliberate choice from the director who is taking his audience from the usual Hollywood slam-bang comedy ambience or has himself gotten a touch of the Epstein-Barr bug. I like to think the former is the case. After a summer barrage of obscene, edgy, heart-pounding, and would-be hilarious fare, maybe this is just the ticket to provide a transition to the fall--which promises to include more of the usual melodrama and highly-paced, strenuously directed moviegoing experiences. Loren Dean's a real find, a lookalike and soundalike for Charles Grodin, and Jason Lee turns in an appealing aw-shucks performance of what Bill Gates could very have been like a decade or so ago. "Mumford" was filmed in Sonoma and Napa County California with all the spirit that has made California the archetypically laid-back locale of the States. Despite that area's wide-open spaces, Kasdan has kept the scenes close and intimate, with generally only two people in the frame at one time. That's all to the good--a restful, realistic remedy for the past summer's wild ride.