However was it that the gods, who have ordered all else so well and with such love for men, overlooked this one thing, that some men, the very best of them, those who had conducted, as it were, the most commerce with the divine and reached the closest relation to it through their acts of devotion and their observances - that these men, once dead, should meet perpetual extinction rather than some return to existence?
Now if this is indeed the case, you can be sure that if it should have been otherwise the gods would have made it otherwise: because if that were right, it would also have been possible, and if in accordance with nature, nature would have brought it about. Therefore the fact that it is not otherwise (if indeed that is a fact) should assure you that it ought not to be otherwise. You can see for yourself that in raising this presumptuous question you are pleading a case with god. But we would not enter such debate with the gods if they were not supremely good and supremely just: and if that is so, they would not have let any part of their ordered arrangement of the world escape them through neglect of justice or reason.
In chapter 4 of Book 12, Marcus focuses on what how we should view our internal thoughts - the ongoing dialogue we have with ourselves. He observes that despite people loving themselves so much, that love stops where begin to judge ourselves. We think less of our own thoughts than we do of other thoughts. We are so ashamed of our thoughts and we are worried about what others might think of us if we were mandated to broadcast our thoughts all the time. I think the correct paradigm would be this: have right thoughts (think of the virtues at all times and apply the discipline of assent at all times and think about the dichotomy of control) and be ready to answer the question, "what are you thinking?" at any given moment and feel no anxiety or embarrassment.
Chapter 5 of Book 12 is more musing by Marcus about the permanence of death. His reasoning is that if the gods don't allow even the best of us to live on, then no one lives on past death.