Mill, J.S., Principles of Political Economy, in Robson ed., The Collected Works of John Stuart Mill,  Toronto: University of Toronto Press, 1963-.

Excerpt:

It appears to the present writer, that a work similar in its object and general conception to that of Adam Smith, but adapted to the more extended knowledge and improved ideas of the present age, is the kind of contribution which Political Economy at present requires. The “Wealth of Nations” is in many parts obsolete, and in all, imperfect. Political Economy, properly so called, has grown up almost from infancy since the time of Adam Smith; and the philosophy of society, from which practically that eminent thinker never separated his more peculiar theme, though still in a very early stage of its progress, has advanced many steps beyond the point at which he left it. No attempt, however, has yet been made to combine his practical mode of treating his subject with the increased knowledge since acquired of its theory, or to exhibit the economical phenomena of society in the relation in which they stand to the best social ideas of the present time, as he did, with such admirable success, in reference to the philosophy of his century.
Such is the idea which the writer of the present work has kept before him. To succeed even partially in realizing it, would be a sufficiently useful achievement, to induce him to incur willingly all the chances of failure. It is requisite, however, to add, that although his object is practical, and, as far as the nature of the subject admits, popular, he has not attempted to purchase either of those advantages by the sacrifice of strict scientific reasoning. Though he desires that his treatise should be more than a mere exposition of the abstract doctrines of Political Economy, he is also desirous that such an exposition should be found in it.

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