What is the old Adam or sin nature?
The old Adam, or sin nature, is the personality with which Adam was created, which became a sin nature when he ate. It has only one bent: rebellion against everything God instructed, taught, or admonished. It answers God with 'No,' reflecting Satan's opposite response.
Les explains that Adam was created with body, soul, and spirit, and in that spirit he had fellowship and communion with the Creator. When Adam sinned, his spirit died, though he did not die physically for 939 years; it became dormant, like a tree in winter or a run-down car battery awaiting outside energy. At that same time, the personality Adam was created with became a sin nature—the old Adam. Les says it has only one bent: rebellion against everything God instructed, taught, or admonished, answering God with 'No.' This pattern is visible throughout human history: what God says for our good, Satan says the opposite.