Firstly, its essential structure forbids dissolution by death.Death is the disintegration of parts. Only composite things can die. Yet the soul is not composite. Its power of pure immaterial thought proves its independence of matter. It is endowed with spiritual faculties, and is as spiritual as the faculties it possesses, which will enable it to live and operate when separated from the body. Not being material, it can never be destroyed or fall to pieces like matter. Nor would God endow it with a nature essentially fitted to live on just for an idle freak, and with the intention of annihilating it after all.
Secondly, every individual experiences a sense of moral obligation, and every obligation demands a sufficient sanction. If the State said, "This is the law," and I replied, "What if I do not observe it," it would be ludicrous were the State to reply, "Oh, nothing will happen. I say only that it is the law. If you break it, you break it, I suppose." That would be a joke, not a law. I know that I shall have to answer some day for my attitude towards the interior sense of moral obligation. I can go right through this life without encountering anyone capable of judging me concerning it. The real answer must be given at the judgement seat of God, and my soul will have to be there. Consequently it must survive.
Thirdly, a more universal view of human life shows us the many inequalities which offend against the sense of justice. We know that justice will be done some day, and as it is not always done in this life, it will be done in the next. This implies our presence, and therefore our living on after death. Fourthly, every soul naturally has an insatiable natural desire for happiness, and for lasting happiness. No earthly or temporal good can satisfy this hunger. Yet this innate natural tendency cannot lack its rightful object. As well try to conceive the existence of the human eye, perfectly adapted to sight, yet without the possibility of light anywhere to enable it to see.
Reflection, then, upon the simple structure of the soul, upon the future administration of the sanctions attached to the moral law, upon the rectification of worldwide inequalities, and upon the teleological inclinations to a lasting and perfect good, makes it a violation of reason to deny the survival of the soul.