The reason I developed my thinking skills in the first place was so I could answer the important questions I saw plastered all over newspapers.
While I now know how generally useless journalists really are, at least their modern species, they nevertheless communicated some interesting questions to me.
The reason I wanted to answer important questions is of course a complete mystery.
The two questions that pop out of my availability bias* as most important are "What is the purpose of life?" and "What does it mean to be human?"
*(Contra cognitive psychology's basic assumptions, biases are quite useful, as long as you know what they're good for.)
The evidence suggests that philosophy is in a sad state. (These are even recursive, which I'll discuss later.) The sad state of philosophy is highlighted by these newspaper profundities, because they're actually very easy to answer. Straightforward, at least.
The meaning of life is happiness and choice.
The proof is simply this: what one thing do humans strive for simply for itself? Happiness. How? By actions they choose themselves.
There! I apparently just owned every philosopher in existence. But, just perhaps, the short version isn't quite satisfying? :-)
A true theory has to be consistent with reality. This can be very helpful with problems like this one, because direct investigation is really hard. Predictions based on any hypothesis of the purpose have a fatal flaw - all the evidence is subjective. This is true even for much simpler machines than a hominid. In archeology, figuring out the purpose of some artifacts can be hellishly difficult, as there's no objective test. The fact we can do it at all is very interesting, and I'll go into it later.
Since the theory has to be consistent with reality, it's worthwhile to simply come up with a bunch of theories, and take the one we can't eliminate as true.
I'm using generalizations, of course, because much of the theorizing has been variations on a theme, and I'm going to eliminate whole themes at once. Taking this approach, there's only three themes.
Onto the proofs.
First, if there really is some sort of benevolent overlord, whose purpose may be mysterious, it doesn't matter. Humans all strive for happiness anyway, so talking about the 'true' purpose is quite pointless - it's not getting done. It's exactly like speeding. Talking about the posted limit is kind of silly if you're trying to explain traffic. You need to talk about the speed, the action, that they're actually undertaking.
Second, if that overlord is in fact running the show, with their noodly appendages reaching into every facet of life, imposing, top down, the values that they hold, it's also irrelevant. This theory is just passing the buck - while human happiness drives may be illusory, the puppet-master still seems to value human happiness, as all their puppets are striving for it.
Third, you are your own overlord, in which case you define your own purpose.
Humans are free, humans are serfs, or humans are slaves, the purpose of human existence is still happiness. Even if humans are some kind of dream and don't really exist, no one has come up with a reality where the real actors aren't somehow scheming for their happiness.
The real purpose is somewhere in the hybrid of happiness and choice, because our choices create the world. While I stole this idea from a hardcore Subjective Reality type, even a hardcore logical positivist has to concede the point. Certainly, the laws of physics are not open to the decisions of its conscious fruit, but our world most certainly is. Nearly everything in your environment has been profoundly altered by the choices of some entrepreneur or another, not to mention the efforts of philosophers regarding your interpretation of these things and events. Finally, unless you were just born, the things and people around you have been profoundly influence by your conscious actions.
I'm currently in an apartment I chose, working on a computer I essentially commissioned, surrounded by furniture I placed myself, not surrounded by anything I chose to throw away. The state of all my money and relationships have been almost entirely decided by how my beliefs affected my actions.
While it would be nice if I could add, "In a jurisdiction I myself endorsed," and "In a neighbourhood of which I approve," these are relatively minor impacts on my life.
I've noticed but cannot prove that almost everything that people say is beyond their control is actually well within it, and the few things truly beyond gain stature by their very difference.
It's similar to the childhood dark ritual of ridicule. Children make fun of someone who is noticeably different in a small way. They don't make fun of plants, or dogs, or even other apes, and this isn't simply because they can't understand. It's because the outsider is different in so few respects. Similarly, the worst warfare is between similar governments, such as sectarian disputes. Protestants don't make war on Hindis. They're simply too different - it provokes disinterested non-understanding, not violence. At least, they don't get nearly as upset by Hinduism as by Islam, or by, heaven forbid, those commahippajewanaziist Catholics.
With this theory, if you agree with me, you know why people value freedom. A person is never going to pursue a course of action they think will lower their own happiness, so any outside interference automatically means that their expected happiness will decrease. There's not a single shred of evidence otherwise, though it can be hard to see. I will happily go through any example you care to bring up.
If you're feeling astute today, you may have noticed that I have completely neglected an important point.
One interpretation of the reason people want to know the purpose of life is so that they can compare it to the purpose of, say, a brick.
The purpose of a brick is to build walls, that's why they're made. The purpose of life is to ____ that's why it was made. While you can use a brick to hold a door or papers, it's better to get a doorstop or a paperweight. Similarly, a life can be used for nearly anything, but it's better to use it for ____.
The problem with this approach is that there isn't any objective creator of life. The universe is not, as Alan Watts says, a pot. It wasn't made by a potter for a purpose, nor does it need to be constantly tended by that someone. It's probably also not the updated fully automatic model that runs all by itself, axiomatically. Nevertheless, there's no way that we know of to prove that the universe isn't just some automaton, such as some message from the creator of life about what to do with yours.
Regardless, such a message would be part of the buck-passing scenario. What would be the purpose of this putative creator's life?
Indeed, the best way to manage a conscious life form is simply to make it want to do whatever its purpose is. As such, if humans do have, in some sense, a creator, unless that creator is a dumb fuck, the best thing to do is simply whatever you want. The creator could also be sadistic, I suppose. Not malicious, as some people put it. When my writing isn't saying what I want it to say, it's not my enemy, 'malicious' doesn't quite describe the feeling.
Nevertheless, with a machine as complicated as a hominid brain it takes some sophistication to even do what you really want properly, but this is just a detail. A very interesting detail I wish to discuss later, but just a detail.
Indeed. What is the purpose of searching for the purpose of life? Quite simply, people think that they'll be happy once they've found their purpose.
Unless, of course, the purpose is forced on the people - the people have to freely choose to follow their immutable purpose. :-) But, again, this is a topic for a later time.
So go forth, equipped with truth, and find or forge your own happiness. Do what you want to do, what you need to do, and don't let anyone tell you otherwise.