We expound an alternative to the Copenhagen interpretation of the formalism of nonrelativistic quantum mechanics. The basic difference is that the new interpretation is formulated in the language of epistemological realism. It involves a change in some basic physical concepts. The $\psi $ function is no longer interpreted as a probability amplitude of the observed behavior of elementary particles but as an objective physical field representing the particles themselves. The particles are thus extended objects whose extension varies in time according to the variation of $\psi $. They are considered as fundamental regions of space with some kind of nonlocality. Special consideration is given to the Heisenberg relations, the reduction process, the problem of measurement, Schr\"odinger's cat, Wigner's friend, the Einstein-Podolsky-Rosen correlations, field quantization and quantum-statistical distributions.