Abstract algebraic logic

The classical method of associating; a class of algebras with a logical system is that of Lindenbaum and Tarski. It can be applied to any system with a biconditional <-> that is compositional in the sense that it defines a congruence relation on the absolutely free algebra of formulas. The method has been abstracted to provide effective criteria for the algebraizability of a large class of formal systems. One consequence of this work is a uniform method of providing a formal system with algebraic semantics. The main features of the theory of abstract algebraic logic and one of its potential applications are surveyed.