BOOK REVIEWS

L. I. SCHZFF, Quantum Mechanics. Second edition. McGraw Hill B0ok CO, New York," Toronto, London. lg55~ xii-417 pages. $ 6.50.

PH. PLUVXNAGZ, Eldments de Mdcanique Quantique. Masson et Cie, Paris.,1955. xii-547 page~. 4.600 French ft.

These two textbooks on quantum mechanics deserve some mention in view of their general excellence. Schiff's wellknown treatise now appears in a second edition which is substantially the same as the first. In particular the author .has wisely resisted the temptat ion to replacing the account of quantum, el.ectrodynamics on traditional lines by a presentation of the new-fangled covariant techniques, which do not belong' in an introcluctory book of this type.

Professor Pluvinag'e has pro-vided French-speaking students with a much-needed textbook of outstanding quality. In fact, his book may Claim universal interest in view of the elegance and lucidity of the exposition.

In neither of these books, however, do the foundations of quantum mechanics receive adequate treatment. Schiif's discussion is much too condensed to be really enlightening. With regard to Pluvinage, ' the cartesian spirit of which the French are so proud (acc0rding to the publisher's prospectus the French reader is "cart6sien de nature" !) has. played him tricks. The analogy wit h c.lassic~ statistical mechanics which he takes as his starting-point is of cgurse quite misleading and in any case unsuited to illustrate the dialectical, utterly non-cartesian character of quantum theory.

L R .

A. LAND~, Foundations o/Quantum Theory, a study in continuity and symmetry. Yale University Press, New Haven. 1955. viii-106 pages. $ 4.00.

Would this small book by a distinguished pioneer of quantum theory provide the needed introduction, into the foundations of this theory? Most unfortunately this question must be definitely answered in the negative. The intrusion of meta- physics into epistemological problems, which ought to be treated in a rigorously scientific way, seems to be a plague of our times. There are those cartesian phy- sicists who take Determinism as their creed. Professor Land6 chooses to invoke, of all people, Leibniz, and invites us to be 'guided by the creed that the world n o t only is the b e s t . . , but also the simplest of all possible .worlds'. He would reduce the infinite richness of atomic laws to the shkdowy Leibnizian principles of con- t inuity and symmetry. When he ventures so far into thin air even the best of all possible physicists must lose control of reality. Professor Land~ has, I amafra id , made a muddle of a perfectly clear situation.

The first confusion arises when he suggests a connection between the statistical aspects of quantum mechanics and thermodynamics. There is of course no such connection in reality; Professor Land6's considerations are of a purely formal nature and they do not receive any concrete contents simply by the use of the word 'entropy'. Moreover, the alleged principle of continuity of entropy by which the author wants to remove Gibbs' paradox in thermodynamics would be tantamount to denying the very existence of atoms and molecules; and the author's ingenious a t tempt to establish a formal connection between this principle and the idea of probability amplitude in quantum mechanics involves too much arbitrariness to be convincing.

As regards the symmetry principle and the restriction of identical particles to symmetrical or anti-symmetrical states, the situation is hardly better. In any