"As for slavery, there is no need for me to speak of its bad aspects. The only thing requiring explanation is the good side of slavery. I do not mean indirect slavery, the slavery of proletariat; I mean direct slavery, the slavery of the Blacks in Surinam, in Brazil, in the southern regions of North America. Direct slavery is as much the pivot upon which our present-day industrialism turns as are machinery, credit, etc. … Slavery is therefore an economic category of paramount importance."

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The particular aspect of history which both attracts and benefits its readers is the examination of causes and the capacity, which is the reward of this study, to decide in each case the best policy to follow. Now in all political situations we must understand that the principle factor which makes for success or failure is the form of a state's constitution: it is from this source, as if from a fountainhead, that all designs and plans of action not only originate but reach their fulfillment.

— Polybius