The Algebra of Logic, being the science of Necessity and Probability, supplies a variety of methods of great power for solving problems in the theory of Probability. I propose to bring before the Society a few examples extracted from my work on the “Principles of the Algebra of Logic,” which is about to be published. A large class of problems, some of which have created considerable diversity of opinion among mathematicians of eminence, can be solved by means of a single theorem.