Carbon is unique among the elements in the number and variety of the compounds which it can form… it is the basis of all forms of living matter. Moreover, it is the only element which could occupy such a position. We know enough now to be sure that the idea of a world in which silicon should take the place of carbon as the basis of life is impossible.British chemist Nevil Sidgwick, Chemical Elements and Their Compounds, vol. 1, p. 490.
For more information about the unique properties of carbon, and how they make human life and the life of other organisms possible, view The Privileged Species or read Chapter 5, “The Fitness of Carbon” in Michael Denton’s book Nature’s Destiny.