I notice that there are still a lot of atheists who attempt to attach some sort of mystical purpose to their existence. For example, there is the claim that we are the instruments by which the universe discovers itself, or that we are here to find out the nature of our existence (a purpose thwarted by covering up the facts with religious fairy tails).
I do not know where this want for an external purpose comes from. Perhaps it is some left-over brain program from our childhood where we are inclined to prefer the values of our parents. Perhaps it is something that is taught from one generation to the next without stopping to consider the wisdom (or foolishness) of doing so.
Whatever its source, there is no external purpose and, even if there were, it would not have any special significance.
With respect to the above case – the universe has no desires. It particularly has no desire to discover itself, Furthermore, it has no means to create us as an instrument for discovering itself.
Finally, even if all of the above claims were false, why would it be more valuable to be an instrument or tool being used by another for the fulfillment of its own desires? This is akin to valuing slavery or rape – because the slave and the rape victims are also treated as mere instruments for the fulfillment of external desires.
To see the problem with this idea that an external purpose is somehow necessary for a life to have value, I imagine that the universe is some sort of reality show.
Imagine that some omnipotent being who was bored with his life seeking some entertainment. He creates a planet and populates it with people who he has made disposed to split up into tribes that go to war with each other.
To help matters along, he appears in different ways to different people telling each of them, "You are the chosen ones. You have the one true religion. Everybody else is a bunch of infidels." All of this is then designed to set up conflict and war. God then sits down on his heavenly recliner with a bag of chips and a beer to watch and see who wins.
If this story were true, we would have our external purpose – our divine "reason for living". However, it does not follow from this that there is any greatness to be found in sacrificing ourselves for God's amusement. The claim, "You must believe in and obey God because, without God, our life would have no meaning and purpose," falls flat if that meaning or purpose is to have a bit part in the ultimate game of Survivor Earth.
The relevant facts are
(1) There is no external purpose to our being here
(2) Even if there were an external purpose it would have no special claim to our allegiance,
(3) If there were an external purpose, and it was a good purpose, the drive to adopt that external purpose is still internal.
There is no justification that a person who serves an external purpose has a better life than one who does not. Even if an external purpose has value we are still trapped by the need for an internal desire to serve that external purpose.
No matter what we do we cannot escape the fact that, ultimately, our motivation and the purposes we serve are internal, not external – or external only in the derived sense of being an external object of an internal desire.
Consequently, it makes no sense to say that a life governed by an internal purpose is "empty" and "meaningless" on account of this absence of some type of external purpose. Indeed, a life spent in service to an external purpose can be even more meaningless and empty. However, even a person who finds value in ‘serving God’ or ‘helping the universe discover itself’ or some other external purpose is still merely following an internal desire to do so.
It can be downright evil.
Even in the absence of an external purpose, there are internal purposes that people generally have reason to promote or to inhibit. However, when we talk about the reasons that people have to promote or inhibit certain malleable desires, at least we have the advantage of talking about something real. Plus, we have the advantage of talking about something where we are not inclined towards the false belief that those reasons have a special merit above and beyond their status of being other people’s reasons for action.
We come into the world with the opportunity to view a cosmic flash of the universe’s life. We have no external purpose for being here. We are simply here. For now.
But, now that we're here, what are we going to do with ourselves?