The Darwinian theory of evolution through natural selection is beyond a doubt an extremely well established theoretical edifice that satisfies any reasonable conceptual and empirical criterion of scientific respectability. It is a body of well confirmed nomological generalizations with great explanatory and predictive power. And yet the most accessible account of the relation between this theory, its competitors and the empirical evidence seems seriously defective in its account of these relations. Indeed, it may seem so defective as to leave the question open, not whether the theory of natural selection is well confirmed (this cannot be doubted), but exactly what sort of evidence does confirm it and via what bridge principles. The account of the matter which I have described as most accessible (in the philosophy of science at any rate), and yet seriously bedeviled is to be found in Michael Ruse's otherwise excellent introduction to the Philosophy of Biology (Ruse 1973 ).