The ability to make decisions and distinguish between what is right and what is wrong come from the brain. In the case of Phineas Gage, who’s brain was damaged by a three and a half foot rod, his ability to distinguish between right and wrong may have been lost. Gage may not have been responsible for his actions after the accident because of the damage that the rod caused. It is possible that the neurons rewired themselves and created new pathways that led to a new way of reasoning.
He could have believed that he was behaving the way he should because his reasoning was changed. Because our actions are controlled by our brain, Gage was being controlled by his brain damage. The loss of part of his frontal lobe may have meant the loss of his decision making abilities as well as a part of him that made him human. Our ability to be rational is part of what separates us from animals, it is what makes us “human”. If that rationality is found in the part of the frontal lobe that Gage lost, he cannot be held responsible for his aggressiveness and unexplainable behavior.