Is there in contemporary scientific cognition baconian "experimentum crucis"?
The paper is dedicated to the role of «crucial» experiments in the development of natural sciеnce. It is shown, that investigation of this problem is part of a more general question - the search of the laws of science development. In the second part of the XX century, with the creation of new physical theories - Quantum Mechanics, STR and GTR (Special and General Theories of Relativity) - this problem moved to the forefront in methodological investigations. The key moment of the paper is differentiation bettween two types of experiments - «crucial experiments» and «experimentum crucis». The last one was introduced by one of the creators of New time science Frencis Bacon. According to Bacon, his experiment was stronger than crucial in solving the problem of theory change. The paper analyzes the experiments of Th. Young and O. Frenel in the theory of light, experiments of A. Lavoisier and J. Priestly in chemistry; the experiment of Michelson-Morly in classical electrodynamics, Bruchawen experiment on checking the hypothesis of the existence of two types of neutrino, and so on. The author of the paper tries to prove, that all these experiments were «crucial», not «crucis», because: they do not satisfy 1) one of the rule of contemporary logic, the so called «modus-tollens»; 2) the logical thesis of Duhem-Quine, and 3) cannot cope with the problem of loadness of experimental data with the verifying theory in the process of its own verification. It is shown in the paper that in real cognition there are many opposite opinions between scientists and methodologists on the role of experiments in the process of verification of a theory. In this connection the question of the very existence of Baconian experiment is discussed.