The theory of defense is analogous to a geology of the mind, linking and clarifying the several layers. Defensive mechanisms have a prescribed, automatic, and compulsive character with a definite direction (toward the interior) and a circumscribed aim (prevention of pain). The ego is to be conceived of as being able to react not merely with one defensive process, but rather with a chain of defensive mechanisms to danger and to anxiety. The chronological genesis of the defenses is still obscure. The totality of the ego organization is not to be confused with the defensive aspects of the ego; these two are not synonymous. There is the hazard of viewing defensive mechanisms as pathologic constructions needing to be destroyed. Very often, on the contrary, the defensive mechanism is an indispensable component of mental functioning.