The article addresses issues related to moral behavior in general and credible moral behavior in the professional activity of doctors and lawyers, in particular. First of all, the most important philosophical views that refer to the evaluation of moral behavior are review end, elaborated by Im. Kant, who believes that moral action, must be based on duty and by J.-St. Mill who evaluated moral behavior based on the principle of opportunity. At the same time, the author refers to likely moral behavior that in principle falls within the limits of morality, but icon the border between moral and immoral. In conclusion, it is noted that doctors and lawyers must know the moral verisimilitude of some professional actions that will help then determine the limit, the frontier, after which immorality begins.