LANGUAGE, TRUTH AND LOGIC is the classic work of philosophy by Alfred Jules Ayer published in 1936 when Ayer was 26 (though it was in fact completed by age 25). This book defines, explains, and argues for the verification principle of logical positivism, as it relates to the use of objectives and methods in determining truths and probabilities. And whether or not one agrees that emperical evidence is the only basis for proof, there is no denying that this is a brilliant book in how it explains in what ways the principle of verifiability may be applied to the problems of philosophy itself. A top read as far as intellectually challenging and satisfying works go.