One approach to the question of which objects discussed by a science are real is to designate as real all and only those entities posited by the most explanatorily powerful theory of the science. But since most scientific theories contain entities posited solely on theoretical grounds, this approach is flawed. Which one of the following principles, if valid, most helps to justify the reasoning above? ['A scientific theory should not posit any entity that does not enhance the explanatory power of the theory.', 'Any object that is posited by a scientific theory and that enhances the explanatory power of that theory should be designated as real.', 'Only objects posited by explanatorily powerful theories should be designated as real.', 'Objects posited for theoretical reasons only should never be designated as real.']