Four well-turned essays, delivered as the Jessie and John Danz lectures as the Univ. of Washington, by the distinguished molecular biologist and Nobel laureate--encompassing the philosophy of science, especially as it pertains to evolution and the human mind. In optimism and eloquence, Jacob compares to Bronowski; he has the same zeal to separate science from myth and religion, the same eagerness to disabuse critics of any notion that science intrinsically supports any body of morals, politics, or ideology beyond the pursuit of truth itself. ""In spite of Dr. Frankenstein and Dr. Strangelove, there are more evil priests and evil politicians than evil scientists."" Unsurprisingly, then, Jacob takes to task some of the more egregious pronouncements of sociobiologists and IQ testers. (Of the latter, he writes: ""How can one hope to quantify such a heterogeneous set of complex properties using a single parameter moving linearly on a scale from 50 to 150?"") Nature is seen, fluidly, as making do and making over. When it comes to distinguishing between human beings and other primates, Jacob generally aligns himself with the neoteny school (exemplified by Stephen Gould), which regards the regulation of genes in development as the differentiating factor between humankind and the chimpanzee, since the DNA complement is so nearly identical. Like many molecular biologists, Jacob views questions concerning embyronic development, particularly of the nervous system, as crucial and challenging; he interprets the mind as an epiphenomenon, growing out of the complex organization of the brain. In the final lecture, Jacob treats the unfolding of the genetic program and its interactions with the environment as leading, inevitably, to the building of a future--apparent in human beings in the biological memories written in the immune system as well as In language and the cultural constructs that lead to imagination and invention. Natural selection and sexual reproduction assure a diversity that allows coping with the possible, while scientific attitudes intervene in a dialogue between the possible and the actual. Hence, we cannot afford to glorify science as ""not merely necessary but sufficient""--nor dismiss science as insufficient and thus unnecessary. A small, rewarding book.