We’re living in an empirical age. The most impressive intellectual feats have been achieved by physicists and biologists, and these fields have established a distinctive model of credibility.

To be an authoritative figure, you want to be coolly scientific. You want to possess an arcane body of technical expertise. You want your mind to be a neutral instrument capable of processing complex quantifiable data.

The people in the human sciences have tried to piggyback on this authority model. For example, the American Psychiatric Association has just released the fifth edition of the Diagnostic Statistical Manual of Mental Health Disorders. It is the basic handbook of the field. It defines the known mental diseases. It creates stable standards, so that insurance companies can recognize various diagnoses and be comfortable with the medications prescribed to treat them.

The recent editions of this manual exude an impressive aura of scientific authority. They treat mental diseases like diseases of the heart and liver. They leave the impression that you should go to your psychiatrist because she has a vast body of technical knowledge that will allow her to solve your problems. With their austere neutrality, they leave a distinct impression: Psychiatrists are methodically treating symptoms, not people.

The problem is that the behavorial sciences like psychiatry are not really sciences; they are semi-sciences. The underlying reality they describe is just not as regularized as the underlying reality of, say, a solar system.

As the handbook’s many critics have noted, psychiatrists use terms like “mental disorder” and “normal behavior,” but there is no agreement on what these concepts mean. When you look at the definitions psychiatrists habitually use to define various ailments, you see that they contain vague words that wouldn’t pass muster in any actual scientific analysis: “excessive,” “binge,” “anxious.”Mental diseases are not really understood the way, say, liver diseases are understood, as a pathology of the body and its tissues and cells. Researchers understand the underlying structure of very few mental ailments. What psychiatrists call a disease is usually just a label for a group of symptoms. As the eminent psychiatrist Allen Frances writes in his book, “Saving Normal,” a word like schizophrenia is a useful construct, not a disease: “It is a description of a particular set of psychiatric problems, not an explanation of their cause.”Furthermore, psychiatric phenomena are notoriously protean in nature. Medicines seem to work but then stop. Because the mind is an irregular cosmos, psychiatry hasn’t been able to make the rapid progress that has become normal in physics and biology. As Martin Seligman, a past president of the American Psychological Association, put it in The Washington Post early this year, “I have found that drugs and therapy offer disappointingly little additional help for the mentally ill than they did 25 years ago — despite billions of dollars in funding.”All of this is not to damn people in the mental health fields. On the contrary, they are heroes who alleviate the most elusive of all suffering, even though they are overmatched by the complexity and variability of the problems that confront them. I just wish they would portray themselves as they really are. Psychiatrists are not heroes of science. They are heroes of uncertainty, using improvisation, knowledge and artistry to improve people’s lives.

The field of psychiatry is better in practice than it is in theory. The best psychiatrists are not austerely technical, like the official handbook’s approach; they combine technical expertise with personal knowledge. They are daring adapters, perpetually adjusting in ways more imaginative than scientific rigor.

The best psychiatrists are not coming up with abstract rules that homogenize treatments. They are combining an awareness of common patterns with an acute attention to the specific circumstances of a unique human being. They certainly are not inventing new diseases in order to medicalize the moderate ailments of the worried well.

If the authors of the psychiatry manual want to invent a new disease, they should put Physics Envy in their handbook. The desire to be more like the hard sciences has distorted economics, education, political science, psychiatry and other behavioral fields. It’s led practitioners to claim more knowledge than they can possibly have. It’s devalued a certain sort of hybrid mentality that is better suited to these realms, the mentality that has one foot in the world of science and one in the liberal arts, that involves bringing multiple vantage points to human behavior.

Hippocrates once observed, “It’s more important to know what sort of person has a disease than to know what sort of disease a person has.” That’s certainly true in the behavioral sciences and in policy making generally, though these days it is often a neglected truth.