I'd like to continue the Open Conversation on The Meaning of Life that Melbourne Philosopher began last month. I agree with him that "The meaning of life is only the meaning that people give to it."
Each person creates their own meaning or purpose in life. It is a necessary truth that we have no externally assigned purpose or function. Free agents are not the sorts of things that can be bound by external purposes. Some people believe that God gives our lives objective meaning. They're wrong. Any meaning their life has comes from themselves, not from God. They have chosen to make fulfilling God's will the purpose of their life. God did not, could not, decide that for them -- not if they were free agents.
But then, what makes doing God's bidding any more meaningful than doing your own, or someone else's? Suppose that God created you for a purpose. Why should you care about that? It does not give your life any objective purpose. It merely has a purpose to God. God's purpose need not be your purpose.
Imagine that I created an army of intelligent, self-aware robots, for the purpose of taking over the world. Now consider one of those metallic free agents. Is it this individual's purpose in life to help me take over the world? Not necessarily. It may be my purpose for him, but thinking agents can rebuke the 'purposes' of their creators. They must, in the end, decide their own purpose in life for themselves.
Even if God existed, he could not do the impossible by assigning objective values to things. If he made us for a purpose, that would merely be our purpose to him. (It remains an agent-relative purpose, even if that agent is God.) A valued object matters to someone, it cannot just matter, simpliciter. That's as incoherent as an object being "lower", simpliciter. (Lower than what? Matters to whom?)
So really the Big Question is not "What is the meaning of life?", nor even the more individualized "What is the meaning of my life?", but rather:
What meaning does my life have to me?
And that is a question that no one else can answer for you. Not even God.