This book traces the development of formal logic from its origins in ancient Greece to the present day. The authors first discuss the work of logicians from Aristotle to Frege, showing how they were influenced by the philosophical or mathematical ideas of their time. They then examine developments in the present century.

Quantum theory predicts that, e.g., in a Stern-Gerlach experiment with electrons the measured spin component $S_Z = \pm \frac{1}{2}$ does not come about by an adjustment at the last moment, a forced “flipping” or “tilting” of the spin (vector), which would imply z-angular momentum exchange between particle and instrument, but will afterward appear to have had the value $\frac{1}{2} or - \frac{1}{2}$ already before the measurement. Because an electron spin cannot have components $ \pm \frac{1}{2}$ in all directions at the (...) same time, the measuring direction has a “privileged” status before the measurement, however we choose that direction, which implies a retroactive effect. A second proof of retroactivity is derived from a special case of the paradox of Einstein, Podolsky, and Rosen. It is strongly suggested by our result that, in essential respects, both Bohr and Einstein were right in their famous controversy about determinism and considering microprocesses “as a whole.”. (shrink)