. ge n - ph ] 2 1 D ec 2 00 5 Theories of Physics and Impossibilities

The role of impossibilities in theories of Physics is mentioned and a recent result is recalled in which Quantum Mechanics is characterized by three information-theoretic impossibilities. The inconvenience of the asymmetries established by such impossibilities is pointed out. Theories of Physics were seen by Einstein as falling into two main categories, [1]. Some are constructive as : " they attempt to build up a picture of the more complex phenomena out of the materials of a relatively simple formal scheme from which they start out. Thus the Kinetic Theory of Gases seeks to reduce mechanical, thermal and diffusional processes to movements of molecules ... ". Other theories can be seen as principle theories, since : " these employ the analytic, not synthetic method. The elements which form their basis and starting point are not hypothetically constructed but empirically discovered ones, general characteristics of natural processes, principles that give rise to mathematically formulated criteria 1