Quantum theory has played a significant role in modern philosophy both as a source of metaphysical ideas and as an important example of a \u27scientific revolution\u27. In spite of the sixty or so years that have elapsed since its invention, a long lasting controversy concerning the interpretation and meaning of quantum theory prevails. Almost all authors, however, seem to agree on one major point, namely, that there could be no interpretation of this theory which is both realistic and local.;The purpose of this thesis is to demonstrate that this premiss is false and that a realistic, local and deterministic interpretation of quantum theory (at least of part of it) does exist, provided that we extend the classical concept of probability.;In...