Montesquieu's "The Spirit of Laws" is an enduring classic of social and political theory deserving a fresh reading every generation. The modern reader, however, is likely to find a work that ran to over a thousand pages in its two-volume first edition a bit overwhelming. Presented here, therefore, is the first English-language compendium of "The Spirit of Laws", together with the first English translation of the posthumously published treatise containing the physiological theory underlying Montesquieu's theory of climate.