Sophus Lie (1842-1899) was one of the most important mathematicians of the nineteenth century. His work on line-sphere transformation and the creation of the theory of continuous groups and his application of these to other areas of mathematics was ground-breaking and has had a lasting effect on the further development in the field. Indeed, a new discipline of mathematics known as Lie theory today has resulted. This unique mathematician Sophus Lie summarized his life and work in the draft of an intellectual testimonial as follows.