5.5302 Russell’s definition of “=” is inadequate; because according to it one cannot say that two objects have all their properties in common. (Even if this proposition is never correct, it still has sense.)

Black (p. 292): “Russell’s definition of identity (Principia, vol. 1, definition 13.01) is based upon the principle of the identity of indiscernibles, which W. is here rejecting.”

Does the proposition in question really make sense? It depends what counts as a property.