The Immortality of the Soul

In laws, Plato outlines in considerable detail the law code of an imaginary city called Magnesia that is designed to be as perfect a political community as there could be on earth. It's not one that Plato ever expected to actually appear on earth in any form, but was holding it out as an ideal as something to strive for at least in part. So this is a suggestive argument for the soul's immortality. Then there's also an argument from opposites. The soul is what animates us and gives us life. And so therefore the very concept of death is alien to it.