Spencer lays down the fundamental rule that the moral conduct of man can be studied scientifically only on condition of being considered as forming part of the conduct in general, and also of the activity in general, of all living beings. Sergi is of the same opinion. And this is correct, Professor Ferri thinks, if, as these two authors do, one studies the conduct and character of man in their constituent elements, in their genesis and development, without taking into consideration the variability of the character, and consequently of the conduct, of man because of his education. In our case, in studying the constituent elements, the genesis, the development, and the variability of the moral part of the character and conduct of man, it is necessary to separate these parts, and to limit ourselves to a special study of one of them. All psychologists are agreed that the moral conduct of a man (including criminal conduct) although having naturally a certain relationship with his muscular and intellectual condition, depends directly and intimately upon the condition of his feelings, emotions, and passions in their moral aspect. Hence it is clear that the problem is: “how far can these feelings be modified by education?” Let us first of all note that the expression, “a man of good (or bad) birth”, does not imply that there are persons who are totally good or totally bad, for these two qualities always appear in combination. It only indicates whether the good or the bad qualities predominate.