profits, and rent will be determined by certain causes; but this class of political economists drop the indispensable presupposition, and argue that these causes must, by an inherent necessity, against which no human means can avail, determine the shares which fall, in the division of the produce, to labourers, capitalists, and landlords. The _Principles of Political Economy_ yielded to none of its predecessors in aiming at the scientific appreciation of the action of these causes, under the conditions which they presuppose; but it set the example of not treating those conditions as final. The economic generalizations which depend not on necessaties of nature but on those combined with the existing arrangements of society, it deals with only as provisional, and as liable to be much altered by the progress of social improvement. I had indeed partially learnt this view of things from the thoughts awakened in me by the speculations of the St. Simonians; but it was made a living principle pervading and animating the book by my wife's promptings. This example illustrates well the general character of what she contributed to my writings. What was abstract and purely scientific was generally mine; the properly human element came from her: in all that concerned the application of philosophy to the exigencies of human society and progress, I was her pupil, alike in boldness of speculation and cautiousness of practical judgment. For, on the one hand, she was much more courageous and far-sighted than without her I should have been, in anticipation of an order of things to come, in which many of the limited generalizations now so often confounded with universal principles will cease to be applicable. Those parts of my writings, and especially of the _Political Economy_, which contemplate possibilities in the future such as, when affirmed by Socialists, have in general been fiercely denied by political economists, would, but for her, either have been absent, or the suggestions would have been made much more timidly and in a more qualified form. But while she thus rendered me bolder in speculation on human affairs, her practical turn of mind, and her almost unerring estimate of practical obstacles, repressed in me all tendencies that were really visionary. Her mind invested all ideas in a concrete shape, and formed to itself a conception of how they would actually work: and her knowledge of the existing feelings and conduct of mankind was so seldom at fault, that the weak point in any unworkable suggestion seldom escapes her.[6]