*Principia Mathematica* has been described as one of the greatest intellectual achievements of human history. It attempts to rigorously reduce mathematics to logic. Among other things, it defines the concept of number. It is obviously a very dense and abstract work which has been made all the more difficult to read in light of more recent developments in the symbolic representation of logical concepts. It would be helpful in any new edition of the book to provide a summary of the reactions to and developments of the ideas in the work, a list of corrections, a bibliography, and a table of equivalent current logical symbols.