Reason and emotion, self-assertiveness and integration, sub-whole and part of a larger whole: Koestler abounds in polarities in this, his summing up of positions taken in his recent psychologizing years. Janus, the two-faced god, looking forward and back, or up and down, is the obvious metaphor for this work of ""schizophysiology."" But it is more schizoid than physiology. Koestler admits to gloomy thoughts; says, in fact, that Homo sapiens has a low life expectancy because of ""the paranoid streak revealed by his past record."" The cause is the inadequate communication between the neocortex and man's phylogenetically older brain(s). A staunch supporter of Paul MacLean's ""horse"" and ""crocodile"" brains (governing emotions and visceral behavior), Koestler simply asserts that evolution has blundered, producing a human brain with imperfect command and control. Never mind that leading neuroscientists are the first to admit that we have barely begun to track the pathways up, down, and sideways in the brain, that the number and function of neurotransmitters are unknown--and that far from writing off the brain as nature's mistake, scientists are just beginning to realize its true sophistication. What would Koestler do? Curiously, having denounced reductionism, materialism, nco-Darwinism, Freud, Watson, Skinner, Monod, Simpson, he opts for a biochemical solution. Drugs will be found that improve cortical control. At the same time, Koestler preaches a neo-Lamarckism, and throws purpose back in biology, as well as mysticism, ESP, Jungian ""synchronicity,"" hidden variables, telepathy. Much of Koestler's writing is authoritarian: he quotes those contemporaries or historical figures favoring his point of view as evidence for its correctness. This gives the book an archaic flavor. Indeed, some of the writing about emotion is as dated as William McDougall or William James. Even terms like ""purposive striving"" are born again. Read in this light, the book has a certain period-piece curiosity. And one essay, on the relations between wit, scientific discovery, and creativity in art, has some striking insights. But read as a work of contemporary science. . . insight into genetics, evolution, and the brain. . . or wave of the future? Decidedly not.