**Born ca. 580**

**Greek philosopher and mathematician**

Pythagoras was a Greek philosopher* who founded a philosophical and religious movement in the 500s B.C. His followers were known as Pythagoreans. Although no written records of his work survive, his teachings influenced several ancient thinkers, especially Plato. Because later Pythagoreans attributed their own discoveries to the founder of their sect* as a mark of respect, it is uncertain how many of their beliefs originated with Pythagoras.

Pythagoras was born on the Greek island of Samos around 580 B.C. To escape the tyrant* of Samos, Pythagoras migrated to Croton, a Greek colony in southern Italy. It was in Croton that he founded his sect, which attracted both men and women. The Pythagoreans followed a distinctive way of life. They practiced abstinence* and were strict vegetarians. They refused to participate in sacrifices*, which were among the most important Greek religious rituals*. Followers of Pythagoras used secret passwords and carried out special burial rites. Pythagoras’s organization angered local inhabitants, who forced him into exile. The Pythagoreans enjoyed a certain amount of influence in southern Italy until the middle of the 400s B.C., when they were violently suppressed. Although their school no longer existed, the philosophical and religious beliefs of the Pythagoreans greatly affected later philosophers.

Some historians believe that Pythagoras introduced the idea of the immortality* of the soul into Greek religious thought. The concept probably did not originate with Pythagoras but may have come from central Asia or India. The Pythagoreans believed that the immortal soul was confined within a mortal body. Trapped in an endlessly repeating cycle, the soul was reincarnated* into plant, animal, and human forms. This cycle was broken by acts of purification. Once the soul had been purged of pollutants, the cycle of rebirth was broken, and immortality was achieved.

* philosopher scholar or thinker concerned with the study of ideas, including science

* sect religious group separated from an established church, usually due to its more extreme beliefs

* tyrant absolute ruler

* abstinence avoidance of certain foods, pleasures, or activities

* sacrifice sacred offering made to a god or goddess, usually of an animal such as a sheep or goat

* ritual regularly followed routine, especially religious

* immortality eternal life

The Pythagorean philosophy focused on mathematical questions and the theories of numbers and music. Pythagoras and his followers believed that all of reality could be explained by mathematical relationships. According to the Greek philosopher Aristotle, even abstract concepts, such as opportunity or injustice, were numbers within the Pythagorean system. Perhaps the most enduring result of the Pythagorean interest in mathematics is the theorem in geometry that bears his name. According to the Pythagorean theorem, the square of the length of the hypotenuse* of a right triangle is equal to the sum of the squares of the lengths of the other two sides.

The Pythagoreans’ work in mathematics was accompanied by advancements in music and astronomy. Pythagoras himself is credited with determining the principal intervals of the musical scale. He discovered that the main musical intervals produced by a vibrating string could be expressed as ratios between the first four whole numbers. For example, the ratio of an octave is 2:1; a fifth is 3:2; and a fourth is 4:3. It was this discovery that may have led the Pythagoreans to explain the universe in terms of numbers and their proportions. They taught that distances between heavenly bodies were divided by regular intervals according to the laws of musical harmony. Some Pythagoreans believed that Pythagoras could actually hear this “music of the spheres.” (See also Cults; Mathematics, Greek; Religion, Greek.)

* reincarnate to be reborn in a new body or life form

* hypotenuse in a right triangle, the side opposite the right angle