This Book is about politics, political theory, and political philosophy. Although these disciplines are often conflated because they interact, they actually are distinct. Political theory is part of political science, whereas political philosophy is a hybrid of political theory and philosophy. The former discipline is descriptive and explanatory, whereas the latter is prescriptive—to the point that it is often called "normative theory." It is in fact the evaluative study of political societies. Whereas political theorists describe and explain politics, political philosophers examine it critically and venture to suggest improvements and, on occasion, radically different social futures. Political philosophers propose scenarios and dreams where political scientists offer snapshots of existing polities. While these disciplines are distinct, Mario Bunge asserts that they must inform each other.

Political philosophy is not yet a well-defined field: it hovers between political theory and utopian fantasizing. Few, if any earlier thinkers could have anticipated any of the most pressing political issues of our time, such as the need to stop global warming, reduce nuclear armaments, stop the rise of inequality between individuals and nations, and fight authoritarianism, particularly when it comes disguised as democracy or as socialism. Not even more recent social thinkers had much to say about such topical issues as environmental degradation, gender and race discriminations, participative democracy, nationalism, imperialism, the North-South divide, resource wars, the industrial-military complex, or the connections between poverty and environmental degradation, and between inequality and bad health.

Beyond ideological divergences, most political philosophers have been nearly unanimous in their indifference to the plight of the Third World. Bunge does not share that indifference. He also believes that political philosophers should pay more attention to numbers, such as the standard index of income inequality and the more comprehensive United Nations human development index for the various nations. It is pointless to write about redistributive policies unless we have some of idea of current wealth distribution. This is, in short a modern treatise of inherited concerns.