If some congressmen had their way, John Hinckley Jr. would be the last American acquitted of a shocking crime on grounds of "insanity."

They probably won't have their way, at least entirely, because extreme remedies tend to throw out the baby with the bath water. But the insanity defense is headed for a timely modification in some jurisdictions. And it looks now as if psychiatrists and lawyers will wisely point the way.

After a special study, the American Psychiatric Association wants the insanity plea restricted to "serious mental disorders," not invoked to protect anti-social people (victims, in their terms, of mere "personality disorders") from the legal consequences of their acts.

Meanwhile, two special committees of the American Bar Association are recommending an important modification of their own. They want the "uncontrollable impulse" plea dropped as a part of the insanity defense. The focus would be on whether the defendant knew right from wrong--a return to the more traditional conception of legal sanity.

For all its recent notoriety, the insanity defense is no great threat to the criminal clearance rate. It is offered in only a minor percentage of criminal trials and is far from invariably successful. But there is a danger that when bad actors escape punishment on the "insanity" excuse, the vital notion of human responsibility may dissolve. Guilt itself may come to seem out of date, with any miscreant deemed more or less sick.

The eminent psychiatrist Willard Gaylin, a leader in the drive to curtail immodest uses of psychiatry in the courtroom, has noted an essential distinction: "The social view of behavior is in essence moralistic; an action is approved or disapproved, right or wrong, acceptable or nonacceptable. A person is guilty or innocent as more or less clearly defined in advance by law.

"But psychiatrically speaking, nothing is wrong-- only sick. If an act is not a choice but merely the inevitable product of . . . past experiences, a man can be no more guilty of a crime than he is guilty of an abscess."

Psychiatry, an immensely valuable medical art making impressive strides in the relief of human suffering, took some rude and ignorant lumps after the Hinckley verdict. It is the wrong target.

Rightly conceived, the debate is over a broad issue of social philosophy. The law, as Gaylin notes, is a social institution. The safety with which it may allow medical (or any other "expert") lore to intrude is always a delicate question. Law is more than a code of behavior. It has its own considered vision of human nature and responsibility, of right relationships between individual autonomy and community duty.

Law rests--indeed, can only rest--on the Aristotelian view that man is a "social animal," whose humanness is largely defined by adherence to society and its ordained standards. It guards individual rights, but flatly rejects the view that human beings can be truly human when they flout duty to others.

There is a compelling argument that recent uses of the "insanity defense" undercut the social bonding function of the law and drive it toward a drastic individualism. The organized bar and organized psychiatry are wise to acknowledge that danger and act on it.