Imagine you're in prison and you ask your cellmate "what's the meaning of us being here?"

If your cellmate is in any way philosophical, they'll ask you to clarify your question, as it is not entirely clear what you're asking. You're probably not, for instance, asking for the meaning of the words 'us being here'.

Let's say you attempt to clarify by saying "I mean, why are we here?" Well, the answer to that one is going to be quite straightforward: "we've all been found guilty of a crime".

Perhaps you want more, though. You ask "but what's the purpose of this - the purpose of our being here?"

Well, to this the answer is a little more complex, though not much. There are three purposes served by your being in the prison. First to protect innocent others from you. You're dangerous. You've proved that. Hence you need to be in the prison. Second, retribution. You did wrong of your own free will and thus you deserve to suffer the company of other wrongdoers. Third, rehabilitation. They're called 'correctional institutions' for a reason: part of their rationale is that by being in them one can learn the error of one's ways, reflect on it, and resolve not to behave in such a manner in the future.

I think the cellmate's answer is also the answer to the question "what is the meaning of life?"

First, if you ask this question, what exactly are you asking?

Well, if asked to clarify you will probably say "I want to know why I am here?" However, the answer "your parents had sex" or 'your parents wanted a child, and so they had sex and here you are" will not satisfy you, will it? I mean, no one disputes these things, yet we still wonder "why are we here?"

So, the question presupposes a grander purpose than whatever your parents were trying to achieve. The purpose of you being here is not, then, conferred by your parents, but someone else. And so to wonder why you're here, is to acknowledge at some level that someone - someone a little grander than your parents - has put you here for some end.

If we assume that the person who has put you here for some end is a good person - and I think they demonstrably are, but for now let's just assume it - then we can safely assume that the end for which we have been put here is a good one.

Yet clearly the world is a dangerous place full of dangerous people. Why on earth would a good person put innocent people in it? Well, "they wouldn't!" is the obvious answer. So they haven't. But a good person has put 'us' here. Conclusion: we're not innocent. Good people do put people in prisons when justice calls for it. And wouldn't it be just to put dangerous people who have done wrong in a world along with other dangerous people who have also done wrong? I mean 'we' think it is just, because that's precisely what we do to people who freely do grave wrongs. We lock them in prison. We surely don't think that reflects badly on us? On the contrary: it is a good thing to do, for it protects others from those folk, it gives those folk what they deserve, and it may operate to help them mend their ways.

So, those who ask "what is the purpose of us being here?" already assume a divine purpose. And if they assume - as they should - that the god who confers purposes on our being here is good, then the divine purpose our being here serves can safely be concluded to be a good one. And I think it is a safe bet that it is justice.

And thus that, it seems to me, is the best and most plausible answer to the question "what is the meaning of life?" The purpose of your being here is threefold. A) it is to protect innocent others from you. B) it is to give you your just deserts. C) it is to rehabilitate you.

Meaning of life: done.