Richardson's Theorem is a result in mathematical logic that deals with the decidability of certain sets of numbers. Specifically, it states that there is no algorithm that can determine whether a given recursive function is total, meaning it produces an output for every possible input. This theorem highlights the limitations of computation and the boundaries of what can be solved algorithmically. The theorem is named after J. F. Richardson, who contributed to the field of mathematical logic in the early 20th century. It is significant in understanding the nature of computability and has implications for various areas in computer science, particularly in the study of formal languages and automata theory.