The eighteenth-century philosopher’s landmark treatise against monarchy that inspired the French and American Revolutions.
 “Man is born free, and everywhere he is in chains.”
 
With these stirring words, Jean-Jacques Rousseau begins The Social Contract—the first shot in a battle of ideas that would set the stage for the American War of Independence and the French Revolution....

The definitive translation of Sun-tzu's timeless classic of military strategy, Art of War
Sun-tzu's Art of War is almost certainly the most famous study of strategy ever written. This treatise has been credited with influencing some of the most legendary military operations. Beyond the battlefield, people far and wide have long turned to Art of War for advice on how to succeed in various competitive situations,...

Explains how scientists' observations of the stars led to the development of the big bang theory, a theory of how our universe was formed.

If a black dog and a white dog have puppies, what color will the puppies be? Genetic scientists have been trying to answer this question for hundreds of years. Genetics is the science of heredity-how traits are passed from parents to offspring. One of the first breakthroughs came from Gregor Mendel, a nineteenth-century monk who spent eight years breeding thousands of pea plants. Pea plants might seem pretty different from dogs, but on a microscopic...

Since prehistoric times, people have wondered how the universe works. Early scientists studied how forces affect objects and watched how heavenly bodies move. In 1687 Isaac Newton published a set of laws that described the motion of all objects, both on Earth and in the heavens. By 1900 many physicists believed only a few questions remained to be answered. But the early 1900s brought revolutionary developments in physics. One was Albert Einstein's...

What is matter made of? Scientists have been trying to answer this question for thousands of years. The concept of the atom-the tiniest fragment of a substance that still retains the characteristics of that substance-goes back to the Greek philosopher Leucippus, who lived in about 450 b.c. In the mid-1600s, Robert Boyle provided experimental evidence that atoms did, indeed, exist. And in 1897, British physicist Joseph John Thomson discovered the first...

How are polar bears related to pandas? For thousands of years, philosophers and scientists have tried to organize and understand, or classify, the relationships among Earth's animals and plants. Early classification systems were cumbersome and inconsistent. In the late 1720s, Carl Linnaeus began developing a classification system to describe relationships among all living things, including animals, plants, fungi, and bacteria. This organization, called...

Since prehistoric times, people have wondered what causes disease. Early people blamed evil spirits. Later, disease was thought to be caused by an imbalance of bodily fluids. By trial and error, people discovered plants that cured certain ailments. But disease still spread through dirty, crowded cities. In 1546 an Italian physician proposed that tiny, invisible bodies cause disease. By the end of the nineteenth century, doctors had discovered the...