Aggressive impulses and behaviour are transient, dynamically changeable tendencies arising in the course of adaptation to inner and outer environments. At times biologically unuseful, unnecessary, aggression is observed with destructive and injurious aims in relation to objects. This can be conceived as the observed result of a dynamic bodily system (the psychic apparatus) reacting to stimuli with characteristic response patterns which are experientially as well as biologically determined.

Destructive aims in certain response patterns (destructive drives) do not inherently reside in the energy which runs the system, but are one of the vicissitudes in the organism's struggle to satisfy its biological needs. Excessive destructiveness is considered not an instinctual need in itself but a maladaptive or misdirected expression of the single instinct to live. The only aim of instinct is to reduce the physiological stimulus, or disequilibrium, and maintain optimal tension, i.e. life.