Quantum Mechanics, Haldane, and Leibniz

There has recently appeared in this journal a very interesting paper by Professor J. B. S. Haldane, entitled, "Quantum Mechanics as a Basis for Philosophy."' The paper might indeed be called, "Leibniz as a basis for Quantum Mechanics." The name of Leibniz does not occur once in the article, yet it is permeated with his spirit, and is just such a document as an orthodox Leibnizian might write should he be confronted with the development of mathematics and experimental science in the two centuries since the death of the master.