  The well known and oft-quoted Feynman's expression, entered the title,
leading at a loss and even being objectionable, has not yet a clear
explanation. The hidden parameters problem in quantum mechanics is considered
here on the base of group-theoretic approach which includes the complete set of
observables indispensably. The last ones are the bilinear Hermitian forms
constructed from the Schroedinger equation solutions and its first derivatives,
they satisfy the algebraic completeness condition. These Hermitian forms,
obtained for the simplest standard problem of particle transmission above
potential step, had been compared with the Hermitian forms which are usually
considered in this problem, and an additional ones, which may be obtained
within the framework of an ordinary schemes of quantum mechanics. It is shown
that the generally recognised schemes of the problem solution lead to violation
of some conservation laws on the step directly. On the contrary, the
group-theoretic approach leads to fulfillments of all necessary conservation
laws everywhere at the same time. It is also shown that the complete set of
observables leads a probabilistic interpretation in quantum mechanics to be
excessive.
