Oft repeated and discussed, Marcus revisits the notion of whether there is a god (or gods) or not. Ultimately, the conclusion is the same whether you believe in god(s) or not. In the end, you will die.
Additionally, if you believe in atoms (randomly governed universe), and if you being a rational and reasonable person, ought not to direct your life at random. Rather, use your intellect and reason to govern and organize your life.
But if you do believe in unity, order and providence, then love it - embrace it. Live life knowing full well that the ultimate directing reason over the universe knows all, sees all and you, as a part of that order, has a part: which is to act well your part; use your reason; live according to nature (meaning, use your reasoning and god-given intellect to live your life). Don't be like beasts who don't reason or think.
(see also Citadel p. 43)