val." Psychiatrist Anthony Storr goes on to insist that aggression is an instinct, and likens it to the sexual impulse - an inherent human trait:
It is true that aggressive tension cannot yet be portrayed in physiological terms as we might describe hunger; that is, as a state of deprivation which drives the animal to take action to relieve it. But the same is actually true of the sexual instinct; and most people, rightly or wrongly, accept the idea that sex is 'an internal driving force which has to be satisfied.' ... In other words, just as with aggression, there is an internal physiological mechanism which needs an outside stimulus to fire it off.
The chief argument concerning this aspect of criminal behavior is that inherent violence only becomes "criminal" in a "contextual" sense; that is, when it violates societal boundaries that are, essentially, artificial. The common example is that of the soldier: violent behavior that is condoned, even rewarded, on the battlefield is grounds for extreme punishment when brought back to the homeland's domestic society. Since the majority of citizens are more or less able to restrain their instinctual aggressive tendencies to fit-in with the artificiality of social rules, "criminality" becomes defined in terms of those who cannot self-impose those restraints.
Following-through on this line of reasoning, recent scientific studies have identified a number of hormonal factors that affect behavior. For example, studies have shown a clear link between high testosterone levels and aggression, although the exact cause-effect relationship has yet to be established. In the other sciences, "father of modern psychiatry" Sigmund Freud made the sweeping assertion that
men are not gentle creatures who want to be loved, ... they are, on the contrary, creatures among whose instinctual endowments is to be reckoned a powerful share of aggressiveness. As a result, their neighbor is for t...