Derb, I think there really is a case for space, though different from those offered by your correspondent. Great powers always expand, in one form or another, and that combined with our frontier, pioneer, city-on-a-hill national character means that we’re always going to be sticking our nose in other people’s business. Other than our ridiculous conquest of the Philippines and Puerto Rico, we don’t do empire like the empires of old, but we’re always going to get sucked into something, whether nation-building in Kreplakistan or liberating Elbonia or bombing tyrants in Pottsylvania. In Madeleine Albright’s immortal words, “What’s the point of having this superb military you’re always talking about if we can’t use it?” And it’s not just an elite thing — there’s also a public appetite for national glory in some form, alternating between forcing democracy on goat-herders and doing social work in Darfur. So a foreign policy based on a limited conception of national interest (which is my own preference, and I think the public’s, despite the public’s simultaneous and contradictory appetite for national glory) is not likely to be sustainable, unless we direct our expansiveness vertically — ad astra.

Great powers of old didn’t have that option. The Persians, Alexander, Rome, the Ottomans, Britain, Russia, etc., etc. could only expand horizontally — you start with Calcutta, then have all of Bengal, then all of India, so you need Suez, so you need Egypt, so you need to protect the Nile through Sudan, so you need to control the headwaters of the Nile in Uganda, so you need Kenya to get to Uganda. It never ends til you run out of gas and in the meantime you’re sucked dry playing nursemaid to rival bands of quarrelsome foreigners.

But in space, there are no quarrelsome foreigners, no one to liberate, no one’s pain to feel, no nations to build, no insurgencies to counter. And the cost is chump change in relative terms — even with space stations and moon bases, we can get twice the national glory at half the price. And we can “leave barbarians alone to practice their unspeakable folkways,” always maintaining the ability to smash them when necessary.

Now there are lots of people who want to do both: try to remake the world in our image and send men to Mars, and I agree that isn’t going to happen. But any effort at shaping a foreign policy that avoids Wilsonian (or Hamiltonian) entanglements needs to provide for an alternative outlet for our enthusiasms, and space fits the bill.