William Gilbert more than 400 years ago formulated a postulate that can be considered as main principle of natural sciences. According to this postulate, the criterion for the correctness of a theory can only be its confirmation by measurement data. In our time, all theories are confirmed by at least some experimental data. But sometimes the theory cannot explain parameters which can be considered as main for objects under study. Usually such “inexplicable” objects and dependencies are called empirical and it is assumed that they do not require theoretical explanation at all. In most cases, this means the fallacy of the used theory. So nowadays postulate Gilbert needs to be reformulated: the correct theory should describe ALL basic properties of objects of research. A number of theories developed in the twentieth century do not satisfy this formulation. In almost all cases, the reason for this is a misinterpretation of nature of objects of study. In particular, in order to satisfy Gilbert’s refined postulate, it turns out necessary to revise the theoretical descriptions: 1) nature of superfluidity and superconductivity;2) nature of neutrinos;3) nature of neutron;4) nature of nuclear forces;5) model of quarks with fractional charge;6) internal structure of stars;7) nature of the Earth’s magnetic field;8) mechanism of thermomagnetic effect in metals.