ARTHUR KOESTLER is a superb performer. Few can surpass the clarity and simplicity with which he can translate complex scientific ideas into common language. Although English is not his native tongue, he is a master of English prose and is a literary figure in his own right. He is the author of a number of distinguished novels and a multi-volume autobiography. Few writers have tried more than Koestler to bring together the values of human existence with scientific modes of thought. His Sleepwalkers , dealing with the Scientific Revolution in the 16th and 17th centuries, showed how the great men of science of that period were also human beings vexed with all the problems the flesh is heir to. In his Act of Creation he drew out with deep insight the similarities between artistic and scientific creation.

Koestler's new book is a summing creation.

Koestler's new book is a summing up and also a continuation of his writings over the last 25 years on the sciences of life. He covers such topics as his theory of hierarchies, creativity in art and science, behaviorism and evolution, free will and determinism, quantum physics, coincidence and parapsychology. He himself remarks that the reader at times will have the impression of deja vu or deja lu . Nevertheless, the book is not only a valuable and interesting summary of these earlier writings, but also contains fresh material and new discussions of vital issues. Now in his early seventies Koestler's brilliance of mind continues undimmed.

The Janus in his title alludes to Koestler's views that every natural entity or "holon" is, as it were, two-faced: it exists as aquasi-independent whole and also forms part of some larger whole; thus man is both a unique individual and part of a social group. This hierarchical order is, he maintains, to be found at all levels in nature - physical, organic, psychological and social; and part of Koestler's objections to determinism is based on this theory. However, when we are told that each such hierarchical level is not simply reducible to a lower level, e.g., that of life, one wonders whether this is not a more elaborate way of expressing our ignorance on this question.

Koestler is critical of reductionism - the view which attempts to reduce human values, meanings and purposes to deterministic structures, and of which he takes behaviorism as a prime example. He is also critical of what he terms the "rationalist illusion" - that everything in nature is explainable. Against this he contends that man's reasoning powers are inherently limited. One may feel sympathetic with Koestler's position here, but this should not prevent us from seeking some rational understanding of man and nature, wherever possible - the alternative is mysticism.

Consider also Koestler's criticism of B. F. Skinner's behaviorism. In Beyond Freedom and Dignity , Skinner protested that Koestler coupled his name with a form of behaviorism 70 years out of date. Skinner has a point here: although cast in the role of the arch-priest of modern determinism, his determinism is not of the mechanistic type and his operant conditioning is more subtle than earlier forms. Determinism for Skinner attempts to trace the regularities which link one piece of behavior with another, and this is not inconsistent with the view that an individual exhibits rational, rule-regulated behavior. Indeed when a person's behavior becomes erratic and unpredictable, this is often a sign of abnormality.

No doubt partly because of his sympathy with te underlog, Koestler is also a strong supporter of what might be termed scientific lost causes - neo-Lamarckianism, parapsychological phenomena and acausality - all of which are discussed in this book. It is likely, as Koestler maintains, that the biological establishment has taken a too hard line on neo-Lamarckian theories of evolution. THere seems some evidence that such theories may be closer to the facts than is usually assumed. Parapsychological phenomena such as telepathy may perhaps lead to the discovery of as yet unknown non-verbal forms of communication. I am more skeptical of the argument that there is an acausal principle, variously termed seriality or synchronicity, which is explanatory of coincidental phenomena. We generally note coincidences when they are sufficiently striking to interest us. The numerous coincidences when they are sufficiently striking to interest us. The numerous coincidences which occur in our daily lives and excite no interest are usually neglected; for these we look for no explanation other than chance. A crucial theme of this book is the moral dilemma of man in the post-Hiroshima period. If we are to continue living a creative, rational existence, we must, Koestler argues, learn to control the more primitive, instinctive side of our nature - otherwise we will end up destroying ourselves and our civilization.