Principle of causality usually means retardation one event relatively another, i.e. necessary (but not sufficient) condition of causal connection. To introduce sufficient condition means to define what observable is the cause and what is the effect. Intuitive understanding of this distinction is suffered in custom use, but in causal mechanics is unsatisfactorily. That is why in causal mechanics formal definition of causality has been introduced, by means of that the principal axiom of causal mechanics then is introduced. The last expresses principle of causality on rigorously formal level. Effect of nonlocality compels to demarcate principle of strong causality and principle of weak causality. Principle of strong causality is : the cause precedes the all possible effects. Principle of weak causality is: the cause initiated by an observer precedes the all possible effects. Nonlocality violates principle of strong causality: the effects of the uncontrolled process-cause can forestall it. By this, value of advancement is equal to classical retardation. Interference of retarded and advanced signals may bring to zero lag in nonlocal correlations. Superluminal communication does not contradict, however, relativity so far as there is not any real motion of the particles (momentum transference). Moreover, there is not in the strict sense superluminal information transference, so far as for it decoding in a receiver (effect) except of the nonlocal channel, in addition a classical local (subluminar) channel must be present. Violation of strong causality does not lead to paradoxes, as advanced effects of only such causes are observed, which the observer can not operate. Advanced nonlocal correlations can, however, be used for forecast of the natural dissipative processes.

S.M.Korotaev