Put on Your Rose-Colored Glasses : POSITIVE ILLUSIONS: Creative Self-Deception and the Healthy Mind <i> by Shelley Taylor (Basic Books: $19.95; 290 pp.; 0-465-06052-8) </i>

Every so often, and generally by accident, the right book comes along to fill a personal need you may not even have known you had. When Shelley Taylor’s “Positive Illusions: Creative Self-Deception and the Healthy Mind” showed up in my mailbox, I was feeling low. The steady worsening of the multiple sclerosis that has crippled me over the last 17 years made it likely that I would soon be unable to leave my house on my own and would thus lose much of the independence I cherish, becoming an increasing burden to my already overextended husband.

Then, in Taylor’s chapter entitled “Illusion, Mania and Depression: A View From Mental Illness,” I read: “Normal people believe to an unrealistic degree that the future holds a bounty of good things and few bad things. Depressed people are more realistic in their perceptions of the future.” Of course ! I thought. I’m depressed ! Or, to use Taylor’s terms, in evaluating the likely consequences of my increasing debilitation, I was suffering from “depressive realism,” “a somewhat more accurate view of reality” than most people take, resulting from “a lack of or loss of the positive biases that normally shelter people from the harsher side of reality.” Having a label for my condition, I cheered up considerably.

Self-deception has long been assumed to be both morally and psychologically unwholesome, a failure to perceive one’s real condition and circumstances, which signals character weakness if not outright madness. In Taylor’s view, however, “rather than being firmly in touch with reality, the normal human mind distorts incoming information in a positive direction.” This distortion, far from being maladaptive, enhances the ability to cope with life’s difficulties and thus actually increases mental health.

The positive illusions involved include self-aggrandizing perceptions of one’s own qualities and capabilities, overestimation of one’s control over circumstances, and an overly optimistic assessment of future events. Drawing on a range of scientific studies, Taylor--who teaches psychology at UCLA--examines these adaptive illusions in the context of everyday life and of extraordinary adversities like rape, tornadoes and cancer. She concludes that “We must view the psychologically healthy person not as someone who sees things as they are but as someone who sees things as he or she would like them to be.”

Taylor’s point is persuasive as long as one shares her fundamentally gloomy vision of reality, and this is hard to reject because she adopts the detached and knowing stance characteristic of much conventional science, which often obscures deep personal bias. She states unequivocally, for instance, that “Without freedom from illness and disability, the enjoyment of other aspects of life is undermined.”

Now, in my experience, disability has actually enhanced my enjoyment of a great many aspects of life (excluding, obviously, ballroom dancing and the like). In Taylor’s reasoning, that enhancement is one of the positive illusions I use to cope with the bleakness of reality. But who is to say that my enjoyment is “really” undermined whereas the enhancement I experience is illusory? Implicitly, Taylor is, because she identifies herself as a scientist and points out that the chief role of science is “to discover and describe truth.” She doesn’t go so far as to capitalize the T, but the point is clear: An absolute discoverable truth exists. And the “real” life it defines is, according to Taylor, so distressing and painful that only the “falsely positive nature” of our illusions can get us through. For some of us, truth just isn’t that easy to come at--and reality just isn’t that bad.

Although thus grounded in a grim view of human existence, “Positive Illusions” is not a discouraging book. It is generally brisk and authoritative and occasionally amusing. Ninety percent of the drivers in one survey, Taylor informs us, believed their driving skills to be above average. Think about that the next time you’re trying to make a left turn through a major intersection at rush hour.

Unfortunately, the prose, though clear, is often tedious: The phrase illusions about the self, the world, and the future occurs so often that I began to wince each time I saw it. Taylor may repeat her generalizations irritatingly because she hasn’t found a way to develop them in lively detail.

For the most part, she summarizes research studies. Although she occasionally gives specific examples, these tend to be brief. Had she expanded these, after the manner of Cheri Register in “Living With Chronic Illness” or Maggie Scarf in “Unfinished Business,” for example, she would have dramatized her points, and at the same time absorbed the reader’s attention more fully.

The lesson here, I suppose, is that a book needn’t be especially well-reasoned or well-written in order to serve as the “right” book. It need simply intersect meaningfully with the reader’s own experience. Taylor’s overview of the healthy human being in “Positive Illusions” is sufficiently broad--as well as good-natured, responsible and reassuring--that the book should be “right” for a good many of us.