A central thesis of much work in Artificial Intelligence is that certain sorts of computational processes provide a good way to represent many of the processes we call thinking, seeing, reasoning, speaking, learning. But what sorts of computations? Not only the manipulation of numbers found in much scientific and engineering computation, but also a wide variety of non-numerical symbol manipulations. Intelligence seems to involve the manipulation of many kinds of symbols that can be used to store information about many kinds of things and their properties and relationships.
The role of symbolic and non-symbolic processing is the subject of considerable debate among those interested in how intelligent systems work. For now, we shall avoid getting embroiled in such debates and merely point out that for many purposes where symbolic manipulation is useful, lists can provide a powerful and general representation. They can also be used for programs operating on numerical data, though in that case some other representation will often be more efficient and more natural, e.g. arrays or vectors.