The author of pioneering results in modal logic while still in high school, Saul A. Kripke continued to develop and extend these insights in subsequent technical work. With "Identity and Necessity" and Naming and Necessity — two published lectures given in the early 1970's that became classics almost upon publication — his work turned towards the philosophical implications of his formal investigations. Then and now, his work is marked by formal rigor coupled with an engaging and accessible prose style. Saul Kripke is Distinguished Professor of Philosophy and Computer Science at The Graduate Center, CUNY, and Professor Emeritus at Princeton University.