The article examines interactions in the system of «subject and object». It is demonstrated that the interactions take place under conditions of a bigger or smaller degree of uncertainty which is still constantly present and which has to be overcome, otherwise the subject’s existence, as it is, becomes impossible. Mind and conscientiousness are interpreted as evolutionally formed mechanisms («instruments») to overcome uncertainty. The very process of uncertainty overcoming is viewed in general from psychological positions. It is proved that a mind bearing person faces uncertainty not only in external, objective world, but also in his inner, subjective world which, too, is overcome by formation of personality.