Pareto first expounded the subject matter of these volumes in the form of lectures that were delivered orally and taken down stenographically. Many traces of that origin survive in the body of the printed Italian text. In this translation I eliminate them. Pareto also makes frequent remarks as to the mechanism Of his book or as to his manner of developing his thought. Such comments I regularly throw into footnotes, and in so doing I merely general ize a device that Pareto used to an extent himself. Pareto's original contains a number of repetitions. These too I eliminate, barring exception, inserting cross-references if anything is to be gained by them. In cases where substantial departures from Pareto's text are made, I warn and explain in footnotes.