Such a tempest! We trusted him to lead in Iraq and Afganistan, we trusted him to run Secrets Central (the CIA), but now many don't trust him because he had an extra-marital affair so they believe it's appropriate that he resign the CIA. I suppose some people think he might not have been able to keep state secrets from another military person, his alleged lover, and the secrets would spill the pillow with security breaches, loose lips sinking ships, whispered nothings becoming something, deep cover uncovered, mistrust=mistress, blanket exposure, and more. The best predictor of the future is usually the past. His record of keeping secrets would seem to have been sterling enough to support his ascendency to top military commands and CIA Director. The allegations of cyber-stalking raised concerning emails to a third party apparently from Petraeus's alleged, and now former mistress, may be serious but there seems to be no involvement of the general. He seems guilty of no more than an extra-marital affair and joins a long list of some of America's most admired and even revered leaders, with literally a tradition of extra-marital affairs! I don't condone it, but history speaks for itself.
In the last 100 years, three of the most admired military leaders, Generals Eisenhower, MacArthur and Patton, had affairs. These seemed bold, self-confident, innovative risk-takers who changed history. General Petraeus's leadership abilities have recently been compared to those of Eisenhower. At the top of the political ladder, FDR, JFK, Clinton, all had affairs, and the first two historically are nearly always in American's top heroes lists in surveys, and Clinton is presently one of the most admired global leaders. In all my decades-long study of heroes and heroism, I have concluded that probably the most consistently admired and seen-as-heroic American public figure of modern times is Martin Luther King, Jr., who, as we know, had at least one extra-marital affair.
In many of our leaders, in public life and the military, I believe an analysis of the job requirements suggests some common qualities, a recipe, if you will, that may vary somewhat in ingredients from leader to leader but often shows such common ingredients as risk-taking, capacity to deal with high uncertainty, innovative thinking, thriving on challenge, boldness, self-confidence and belief that they control their destiny, and independence of judgment. Life at the top is not for everyone. I believe it requires many or most of the foregoing personal ingredients; add in the admiration that many people feel for the leader, and you have a volatile mix where a risk-taker meets opportunity in an admirer and an affair happens.
Universal monogamy is a lost cause in our species. Some achieve it, others don't. In the case of Petraeus, his affair was with his personal biographer, a very attractive woman, someone with whom he presumably spent a great deal of personal face time, as well as electronic communication, phone chat, etc. They presumably became close friends, not unlike work-place bonding that can often lead to an affair. She also had a military background, and was a self-described risk-taker, "adventure junkie" her husband said of both of them. The terminology I favor here is "Type T Personality," the T referencing the thrill component of much risky thought or behavior. The meaningful , fully lived life of many leaders in many fields is exciting, a thrill, that keeps them pushing forward into new challenges, making decisions and utterances under public scrutiny that have impact and could make or break a life or career.
Some people have said such affairs are an excerise of power. When one directs the world's most powerful spy agency, I don't think one needs to exercise one's power over a comparatively powerless individual. Some cry "narcissism!" But how exactly self-love translates into such career-risking behavior is unclear.. If you are perfect, you wouldn't want to ever risk such imperfections as a perceived failure of self-control, or such "stupidity." And if you resort to DSM-style definitions, these days you'll be up to your ears in criticism! Others might say its all in some specific brain process, its ocytocin, or dopamine, or other over-generalizations from very limited lab-based small convenience samples of college kids. Or one might resort to the extreme speculations of evolutionary psychology.
For sure we do not know with any certainty what motivates this type of behavior; a lot is speculation. My view has been to consider what kind of people might be attracted to the features of such leadership careers and actually attain them and do extremely well in them. Join the debate!