One can read out of Newman's descriptions a really extraordinary role for this English genius who lived to be only 35 and had just 15 productive years. He died almost is the year Frege and Boole began the systematic restructuring of mathematical foundations, but his work on the specific foundations of all the known geometries represents some of the most acute thinking in mathematics with regard to the relation between geometry and physics. Lord Russell has recalled that his own early work was done in ignorance of Clifford's, but ventured that Clifford in the 1870's was thinking ahead of the best minds of his day. In Einstein's time the geometry of the real world lost its reliability as a frame of reference and became properly a part of physics itself. One can infer from both Newman and Russell that this inversion, an alien notion to most nineteenth-century thinkers was already half-formed in Clifford's mind.

Another prescient insight was Clifford's careful questioning of exactness of measurement:

"The knowledge of an exact law in the theoretical sense would be equivalent to an infinite observation. I do not say that such knowledge is impossible to mean; but I do say that it would be absolutely different in kind from any knowledge that we possess at present."

This sort of thinking was not appreciated until well into this century when physicists began worrying seriously about the limits of measurement.

Newman takes the space and the care of look thoroughly into Clifford's presuppositions; the result is a thoughtful and interesting sketch. The selection on Einstein is shorter but no less satisfying. Einstein's own questions are dealt with fairly in a coherent outline of his discoveries and some of his own classic illustrations. The editor and the expositor in Newman have somehow blended perfectly here.

HE follows these with a group of intriguing reviews on Pascal, Mill, Wittgenstein, and others of more sensibility than science. The discussion of The Age of Analysis picks up Morton White's rewarding distinction between the "hedgehogs" and "foxes" of twentieth-century philosophy (taken from the Greek poet Archilochus: "The fox knows many things, but the hedgehog knows one big thing.")

The subsequent essays built around causality and determinism in modern physics should be all means be read, if for no other reason than to form some impression of the quicksilver state of physics with regard to these concepts. Wave-particle duality and the Heisenberg uncertainty principle are still hard to get used to, but there has for several decades already been a flux of speculation about their meaning. Ernest Cassirer, David Bohm, and Erwin Schrodinger are writing in a realm where it is