There are three main sources of group theory. The first source of group theory was number theory, beginning in the late 1700s. A second source was the theory of algebraic equations, leading to the study of permutations, also beginning in the late 1700s. A third source of group theory was geometry beginning around 1800. | There are three main sources of group theory. The first source of group theory was number theory, beginning in the late 1700s. A second source was the theory of algebraic equations, leading to the study of permutations, also beginning in the late 1700s. A third source of group theory was geometry beginning around 1800. |