Why Colonize Space?

For the sake of argument, let say there aren't any rational reasons to colonize space.   Let's reconsider that in another light by making an analogy.   What if you could compare an off world colony to a child?   What if you could consider the Earth having a son or daughter world that could be born and raised up until it can go out on its own?   Let's consider if that is possible.   Then it can be considered as a choice to do or not do.

Now for the matter of whether or not it could be done.  Let's start with the Moon.  We now know that there is water on the Moon.  There may be other "volatiles" that could be useful in life support.  In addition to all this, there is abundant matter on its surface.   With some effort and expense, a permanent lunar colony could be started which could do...  what?

I think that it should immediately put to the task of creating an artificial world that O'Neil envisioned.   Getting material from the Moon to space is a lot easier from the Moon itself than from directly from Earth.  The advantage is in the same vein as it would be to put a colony on the Moon.  It is easy to escape the Moon, and easier still to escape an O'Neil colony.  From an O'Neil colony, it could then be possible to begin colonizing the rest of the solar system.

The O'Neil colony would be the ultimate goal, but in the meantime, we have to fix up a Moonbase. We need access to its resources, which could consists not only of its volatiles, but also of thorium, which can be used as a source of energy.  Why thorium?  Assuming that fusion is still a long ways off, we know that thorium can be used with today's technology.  Therefore, the second task on the Moon, after mining it for its volatiles, would be to mine it for its thorium.  Now, let's inventory the lunar capabilities.  You have a life support system in place which, with an energy source, can begin major processing of lunar ores.  In short, you can start making stuff for your O'Neil colony.  In addition, with an energy source like thorium, you can have a propulsion system that can get you off the surface.

You need a transportation system on the Moon in order to move materials around on its surface.  This can be achieved with mass drivers, or some similar technology.  In this manner, a lunar trading system can be emplaced, which could move materials from where there are to where they are needed.   Now, you have a life support system, an energy production system, a transportation system, and an economic system.  It is beginning to look like a society that can begin to support itself.  Not to mention, it can cooperate with Earth and create another O'Neil colony in space.  In this manner, the colonies begin to act like an organism that replicates itself.

And that is the whole idea.  Life doesn't have to be "rational" in the sense of always being economical.  If you want a child, for example, it isn't so you can make money off the child.  You want a child to pass along what you know to the next generations to follow.  It is like a bond from the past towards the future.  A society that no longer cares about this no longer cares about continuing to exist.  What kind of world do we want to leave our progeny?  A world in which can be ever increasing and expanding, or one in which is always contracting and dying off?  A colony would be an investment in our own future.  Even more, it can be our guarantee of even having a future.   We may not benefit directly ourselves, but we can be assured that those following us will have a place in the sun.