According to Christian and Jewish theology, original sin is a spiritual disease of the human soul, a disease that is passed on to future generations as much as physical characteristics or physiological defects. Just as genetics pass on physical traits like eye and hair color from parent to child, original sin is the spiritual inheritance passed on to children from their parents, and ultimately from Adam and Eve themselves.
The phrase the Fall is used by Jewish and Christian theologians to describe the consequence of original sin. Prior to their disobedience, Adam and Eve were created and endowed by God with spiritual integrity and sanctifying grace. After they sinned, they lost that integrity and grace, hence the idea of fallen human nature or wounded nature. In other words, they fell from the spiritual level of being in communion with God to the level of being in sin. In turn, sin divides and causes further division.
The point of the story of original sin is not to pick apart the details, but to understand the message. Had Adam and Eve remained obedient, God would have revealed to them what was good and what was evil. But they wanted to know for themselves. Because of their transgression, human beings would have to learn the hard way, discovering good and evil for themselves, instead of being told and believing in what God says. Men and women would have to struggle to discern morally correct behavior.
Bible scholars use this analogy to clarify the lesson: Think of a curvy roadway. Without a speed limit sign to tell you how fast you should go, you have no way of knowing how fast you can drive before your speed becomes dangerous. Without a road sign, you must determine the correct speed on your own and, as a result, you’re at greater risk of getting into a nasty accident.
Before Adam and Eve sinned, God would have functioned as that road sign. Instead, pride caused the first man and woman to drive recklessly, ignoring every traffic code in the book. So they, and in turn humankind, now have to figure things out by using their conscience and their reason, which are not perfect and certainly not infallible.