Mathematical Logic is a necessary preliminary to logical Mathematics. _MathematicalLogic_ is the name given by Peano to what is also known (afterVenn ) as _Symbolic Logic_; and Symbolic Logic is, in essentials, the Logicof Aristotle, given new life and power by being dressed up in the wonderful_almost magical_armour and accoutrements of Algebra. In less than seventyyears, logic, to use an expression of De Morgan's, has so thriven upon symbolsand, in consequence, so grown and altered that the ancient logicians wouldnot recognize it, and many old-fashioned logicians will not recognize it. Themetaphor is not quite correct: Logic has neither grown nor altered, but we nowsee more of it and more into it.