There is clearly room for much difference of opinion in detail here. And yet it will be plain to all that the subject matter of a science must be limited; we must know when our studies begin and end. It is not demoralization which makes an economist deny holiness to be wealth, it is a classification of sciences. Holiness is not matter either, nor electricity, nor gas; it does not come into Physics any more than into Economics. It comes into Ethics and Theology and practical Politics, and it is the most important thing in the world. It may be true, as Ruskin urges, that wealth is not any good to a miser or a spendthrift or a rogue; that it is often I11th rather than Wealth, if it makes its user soft and slack and selfish, or proud and cruel. But nevertheless, it is an object of desire, of human motive; and that is enough for the economist. The mistake of the early economists before John S. Mill was in not recognizing, however, the reaction of man’s possession of wealth upon his conduct as a producer; how high wages might be remunerative, if they increased efficiency, and big fortunes wasted if they increased idleness. We really have to treat two factors, each of which is, in the language of Mathematics, an implicit function of the other--or, if that does not make it more clear--each of which acts upon and is acted upon by the other. The early economists lived in the age when steam engines and electric telegraphs were great and new achievements, when Chemistry was being reborn in the atomic theory, and Joule was proving the great generalization of the conservation of energy. They treated their subject--man in business--as if he were matter; whereas he has biological characteristics, and is modifiable and can modify his environment. Our age, on the contrary, is concerned with the modification of characteristics under environment. It is the age of Darwin. Biological evolution is seen to govern the growth of men and societies; and these, in writings of the dominant school of thinkers since Herbert Spencer, are seen to follow biological laws of growth. The Economic man is no exception.