Those who reject the biblical tenet that teaches humans are born with a sin nature, i.e., hardwired with a desire for unfettered selfishness and rebellion against authority from birth, are left trying to explain all behavior -- from altruism to evil -- by solely cultural or environmental influences.

For those who reject the biblical understanding that human nature is inherently selfish, human nature is essentially good. And if an individual is given a good home and a good education, he or she will turn out to be a good, altruistic person.

In the instance of the Colorado shooting, those who reject the idea of a sin nature want to know all they can about the perpetrator. What was his childhood like? With what groups did he associate? Was he bullied growing up? All efforts seek to look outside the shooter to see what influences caused his murderous rampage.

When a person who has every advantage in life commits evil, immoral and illegal acts, those who believe human nature is essentially good are left scratching their heads, wondering what must have caused the behavior. Such seems to be the case with regard to the Colorado shooter.

Of course, one motive for trying to understand what influenced a perpetrator is the hope that similar events in the future can be thwarted. But that effort is futile. In a fallen world populated by sinful people, evil is an ever-present reality.

Those who accept the biblical tenet that humans are born with a sin nature understand that the cause flows from within. Every person is born broken, with a genetic predisposition to do whatever is in his or her heart, regardless of who is hurt in the process.

Accepting the biblical premise that humans are by nature selfish means understanding they will act upon those self-centered urges. Some will act out violently and others only selfishly. Some even will act in ways that appear to be altruistic, but deep inside it is rooted in selfishness.

Those who doubt the inherent selfishness of human beings need only to observe a 2-year-old. At about the age of 18 months to two years of age children in every culture start to exhibit the most selfish of tendencies.

A 2-year-old does not have to be taught to be selfish or bad. No, a child must be taught and trained to share and to be good. A child has to be taught how to treat others properly and to respect their property. This is the sin nature on display.

Of course, a variety of environmental causes may or may not contribute to how a person chooses to behave with regard to his or her sin nature. That said, an outside force can only influence how a person will act with regard to his or her sin nature -- not if they will act on it. Continued...