This book begins from the premise that a common nature is shared by all human beings, regardless of social or economic background. The author asserts that significant moral consequences flow from the assumption that all human beings share a common set of natural needs. Using this starting point, the book seeks to defend an objectivist epistemology.

This book begins from the premise, which it seeks to elaborate, that the poorest human being shares with the richest, a natural nature. This, it is claimed, is not the trivial thesis it is sometimes represented as being. Rather, significant moral consequences flow from the assumption that all human beings share a set of natural needs. Using this starting point, the book also seeks to defend an objectivist epistemology.