I've found it! At last!
  I have determined what I believe the purpose for our human lives must be.
It is a very simple conclusion, so simple that perhaps I subconsciously
thought of it before and dismissed it as too simple to be a reasonable
defining purpose. But it is the only purpose which makes sense when viewed in
the light of what it means for us to exist.
  Before I state exactly what my conclusion is, allow me to explain the
reasoning process by which I reached it.
  First of all, let us broadly divide human goals into two categories:
  1. Creation of "good".
  2. Elimination of "bad".
  The second category comprises a large portion of human endeavor today, but
upon reflection, it seems like it cannot reasonably serve as a reason for
existence. This category deals with acts that attempt to solve problems in
the world. People who try to find a cure for cancer, people who advocate
peace instead of war, and people who are trying to quit drug addictions are
pursuing goals in this category. They are not actually creating anyting good;
they are only trying to eliminate negative elements in life: Cancer, war, and
addiction, respectively.
  While these are worthy goals which may become important to pursue because
of circumstances, they cannot, in themselves, provide a good reason for
living. Imagine if all the people who were trying to eliminate the "bad" in
the world succeeded: What would they do next? Eliminating cancer, war, and
drug addictions are all acts done to sustain life, but what would the purpose
be in sustaining life if it were only done to live?
  The classic human-extinction scenario would solve all of these problems
instantly. If a global thermonuclear war broke out right now and killed every
living human, there would be no more disease, no more hunger, no more war, no
more crime, no more poverty, and no more drug abuse. The people fighting the
"bad" in the world would have attained their goals.
  This is why I am a little irked when I hear someone say something like "My
life's goal is to find a cure for cancer." While their goal is indeed a
useful one worthy of pursuing, it can hardly define someone's life's purpose,
because they are not actually producing something that makes life worth
living. Similarly, I am usually annoyed when I hear people speak of "peace"
as an end in itself. Of course war is undesirable, but if we had peace, what
would we do with it? Lack of war is not, in itself, a goal for life, because
it does not define anything; rather, it defines a *lack* of something.
Indeed, in general, anyone who defines their life's purpose as the
elimination or destruction of something is probably wasting their life,
because there will always be problems in the world, and if everybody's life
becomes devoted to nothing but attacking problems, then we might as well all
commit collective suicide, because we've already lost any defining purpose to
our lives, and we'd be better off dead since our whole lives are spent
fighting trouble anyway.
  This isn't to say that attacking problems is not a worthy pursuit; not at
all. Everybody has problems, and a certain portion of our lives must be spent
trying to resolve those problems. However, fighting trouble is actually a
distraction from life; it cannot be, in itself, the defining purpose for
life.
  This leads us to the other of the two broad goals I mentioned: Creation of
"good" things.
  This category is largely comprised of the arts. Literature, painting,
music, and film are all borne of creation. When a person writes a book or a
piece of music, they are creating something from nothing; they are producing
a work of art that did not exist before. Of course, much of the arts also
falls into the category of trying to fight problems; many works of art are
"anti-" in nature. For example, they may try to discredit some politician or
some way of thinking. Not all art is done just to add to human knowledge, but
an appreciable portion of it is.
  Similarly, science also helps to create something from nothing. Even though
most research today is usually done with the intent of trying to solve some
existing problem, every scientific discovery humans make adds to their body
of knowledge, regardless of whether we can clearly use that knowledge or not.
You can sit down and read a book about (for example) molecular biology, and
unless you intend to actually become a molecular biologist, you may never be
able to make practical use of any of the information in that book at all.
However, you might still find the information there personally interesting,
and live better the rest of your life simply for knowing the knowledge
contained therein. The simple act of knowing is an experience unique to
sentient creatures.
  Of course, besides knowing things, people often define their life goals in
terms of pleasant feelings, especially love. To "love, laugh, and be happy"
is a very common defining human ambition. Many people also make personal
health a goal. While all of these are, again, worthwhile pursuits, alone they
are doomed to failure, because they are all temporal. Happiness comes and
goes, and no one--even with the aid of powerful illegal stimulants--can be
happy every moment of their lives. Indeed, the harder people try, the greater
their depression when they finally cease being happy. It is the nature of
human beings to experience oscillation in their moods, and sadness is an
integral part of our imperfect lives. Similarly, contrary to what some songs
have claimed, a person cannot "live on love". Of course people should not
live without love or joy, but these emotions, in themselves, cannot
constitute the whole reason for our being.
  Even religion, by itself, is usually not adequate at leading people into
what to do with their lives, because most religion is very general. Most
religion is content to encourage people to "follow" their faith, meaning to
do whatever God (or Allah, or Buddha, etc.) wants. This can also be an
admirable goal, but it immediately and inevitably leads to the question:
"Very well, but what does [deity] want me to do?" If there is indeed a God,
it seems clear that we were made with brains, and it must have been the
intent of our Creator to use those brains for some positive purpose.
  All of this leads me to the following simple defining purpose for we, as
human beings, to exist: To learn and to know.
  These five words, by themselves, are admittedly quite simplistic, and they
could perhaps benefit from some elaboration. For example, it's worth adding
that pure knowledge, by itself, is also not very useful. You might learn that
Napoleon was born in 1769, but this knowledge, in itself, is quite useless,
without some context explaining the circumstances surrounding his birth and
the culture that existed where he was born at that time. Information like
dates and other purely numerical statistics, which alone provide little or no
real insight, are often termed "data" rather than "information", and they are
what computers work with. A computer often "knows" many things, but it has no
appreciation of all the data it holds. For us as human beings, rather than
simply learning things, it's important to emphasize understanding: The
ability to comprehend the information we take in and form insights about it
based on our comprehension. This combination of factual knowledge with
conscious reasoning, understanding, and insight forms the more important
concept of "wisdom". It might then be better to say that our goal, as human
beings, is the attainment of wisdom. (And, of course, to share that wisdom
with others, since wisdom held in loneliness and isolation cannot be learned
or enjoyed by anyone else.)
  Everything else seems to exist mainly to support this goal. We work to earn
a "living", which consists of basic necessities of life such as food and
shelter, but these, in themselves, are merely acts done because they are
necessary; they are not ends, but rather means to an end (unless one can
consider simply being alive an end in itself). We exercise to maintain
health, we make friends so we can share thoughts and feelings, but all of
this is secondary. The one thing that cannot change is truth, and the one
thing that we cannot lose (until we grow old and senile, or suffer from some
brain malfunction like amnesia) is knowledge.
  This goal encompasses all forms of media: Not only classical art categories
like books, music, and movies, but even personal experiences, such as things
one sees during the course of their everyday lives, or conversations one has
with other people. This goal comprises both giving and receiving, for one
cannot read a book without someone else having written it first, nor can one
have a conversation with another person without both speaking and listening.
  Of course, in order for someone to be effective in this goal and enjoy
themselves while pursuing it, they need to have a natural curiosity, an
inherent desire to learn. There are many people who do not; unfortunately,
this lack of curiosity is often created by the experience of childhood
"education", in which children are forced into schools and taught from a set
curriculum which frequently does not interest them. It is through this
process that children are taught, from an early age, that learning is boring
and pointless. In order for anyone to be successful in life, they will need
to cultivate the natural curiosity of the human spirit which is so frequently
squeezed out of people from an early age. If you are not a curious person,
try turning your curiosity back on by gently beginning to explore something
which seems like it might be of interest to you. You just might surprise
yourself.
  Even for people who are naturally curious, it sometimes becomes desirable
to study things which are not of particular interest. Everybody has areas of
specific interest: Some people are more interested in the sciences, while
others prefer art, for example. This is perfectly natural, and it is well and
good for someone to focus on a field that suits their preferred talents and
interests. Even so, one should not restrict themselves, for one never knows
what might be waiting to be discovered in other fields. Every now and then, a
person seeking to lead a life of learning ought to briefly read up on
something, even something which is of absolutely no interest to them
whatsoever, just to keep their minds suitably elastic.
  Oh, and don't forget to have fun while you're doing this; learning and
knowing is supposed to be enjoyable. If you're not enjoying it, you're trying
too hard. Let it come naturally.
  See you in a library.