I came into history from a primary concern with mathematics and science. This has been a tremendous help to me as a person and as a historian, although it must be admitted it has served to make my historical interpretations less conventional than may be acceptable of many of my colleagues in the field.

When goods are exchanged between countries, they must be paid for by commodities or gold. They cannot be paid for by the notes, certificates, and checks of the purchaser's country, since these are of value only in the country of issue.

It is not easy to tear any event out of the context of the universe in which it occurred without detaching from it some factor that influenced it.

When profits are pursued by geographic interchange of goods, so that commerce for profit becomes the central mechanism of the system, we usually call it "commercial capitalism." In such a system goods are conveyed from ares where they are more common (and therefore cheaper) to areas where they are less common (and therefore less cheap). This process leads to regional specialization and to division of labor, both in agricultural production and in handicrafts.

To this day the Arab influence is evident in southern Italy, northern Africa and, above all, in Spain.

Western civilization presents one of the most difficult tasks for historical analysis, because it is not yet finished, because we are a part of it and lack perspective, and because it presents considerable variation from our pattern of historical change.

Capitalism might be defined, if we wish to be scientific, as a form of economic organization motivated by the pursuit of profit within a price structure.