I would say C#, my apologies to John McCarthy, see his papers referenced at his Stanford site, and also I quote from his excellent paper: "LISP-Notes on its Past and Future-1980" in this blog entry. LISP is the classical artificial intelligence language, and really I think that outside of Haskell, it has strongly influenced the formation of object-oriented languages. However, I do not think that LISP meets the needs of the current user of artificial intelligence, and I make that statement with caution and respect for the extensive work that has been done with LISP by the computer science and artificial intelligence pioneers. Times have changed, and the needs of the user, not the developer, is now the main driver of computer science and the more pragmatic information science workers. But with any broad statements that will likely get a response from the one or two readers of this blog, let's take a look at the definition of LISP, as we move toward the programming of AI, it is important that the history of AI is understood, and I could be wrong, so in case I am, you have the references to LISP to get back on track (from the article mentioned earlier in this entry): As a programming language, LISP is characterized by the following ideas: Computing with symbolic expressions rather than numbers. Representation of symbolic expressions and other information by list structure in computer memory. Representation of information on paper, from keyboards and in other external media mostly by multi-level lists and sometimes by S-expressions. It has been important that any kind of data can be represented by a single general type. A small set of selector and constructor operations expressed as functions, i.e. car, cdr and cons. Composition of functions as a tool for forming more complex functions. The use of conditional expressions for getting branching into function definitions. The recursive use of conditional expressions as