Language, Truth and Logic/A. J. Ayer

If you can't prove something, it is literally senseless - so argues Ayer in this irreverent and electrifying book. Statements are either true by definition (as in maths), or can be verified by direct experience. Ayer rejected metaphysical claims about god, the absolute, and objective values as completely nonsensical. Ayer was only 24 when he finished LANGUAGE, TRUTH LOGIC, yet it shook the foundations of Anglo-American philosophy and made its author notorious. It became a classic text, cleared away the cobwebs in philosophical thinking, and has been enormously influential.