On the "Derivation of Einstein's Field Equations, S. Chandrasekhar, Vol. 40, February 1972
An attempt is made to clarify the physical and mathematical reasonings that underlie Einstein's laws of gravitation. It appears that only by a mixture of physical reasonableness, mathematical simplicity, and aesthetic sensibility can one arrive at Einstein's field equations. The general theory of relativity is in fact an example of "the power of speculative thought." The topics considered include a discussion of the principle of equivalence and the view of space-time as a geometric manifold. Two "derivations" of Einstein's equations are given: one based on physical reasonableness and the other based on a variational principle and mathematical simplicity.