Leo Strauss reviews the history of the idea of natural right, tracing its origins among Greek philosophers and bringing it up-to-date through the mid-20th century, when the book was published. It grew out a series of lectures he delivered.

Strauss argues that the idea of natural right has gotten lost among contemporary critiques claiming that universality is not possible. The argument is that

there cannot be natural right if there are no immutable principles of justice, but history shows that all principles of justice are mutable.

One modern philosopher Strauss admires is Max Weber. He sees Weber’s use of historicism as acceptable in part because it did not totally rejected natural law.

He objected to the historical school, not because it had rejected natural norms, i.e., norms that are both universal and objective, but because it had tried to establish standards that were particular indeed, but still objective.

Natural right, to Strauss, is an idea that is essential to political life. While people had engaged in political life, the idea was important to a scientific understanding of what is political. In order to formulate a science of politics, natural right had to be discovered, Strauss insists.

[A] political life that does not know the idea of natural right is necessarily unaware of the possibility of political science and, indeed, of the possibility of science as such, just as a political life that is aware of the possibility of science necessarily knows natural right as a problem.