Here’s a story related to me by another philosopher. The philosopher in question might be labeled “libertarian”, though that label is as misleading as it is helpful. (Indeed, I’m still worried that putting “libertarian” in this blog’s title has been misleading or unhelpful to some of  our commentators.) The philosopher was giving a talk on some particular topic in political philosophy. I don’t recall what the topic was. But like most papers, it made a relatively small point. It did not try definitely to prove or defend a full theory of justice and morality. That’s something you can’t really do in an entire book, let alone a 30-page philosophy paper.

At the end of the talk, someone in the audience asked my friend, “So, how exactly does this prove libertarianism is true?” My philosopher friend was surprised. He said, “It doesn’t.”

The audience member realized his mistake. When a philosopher defends a thesis X, he’s just defending X. The philosopher may also believe Y and Z, but there’s no obvious reason to demand that the philosopher then try to show that Y and Z follow from X. There’s no obvious reason to complain that in defending X, the philosopher did not also defend Y and Z. (If Y and Z are inconsistent with X, that’s a different story.)

So, consider the recent video by David Schmidtz I posted. (The video was aimed at undergraduates, but it has some food for thought here.) Schmidtz relates a thought experiment by Bruce Ackerman. Ackerman says that if you and I both arrive simultaneously at an unowned, unused apple tree with two apples, we both have an equal claim to one of the apples. Ackerman tends to use this thought experiment to argue that in the real world, we’re often due equal shares.

Schmidtz responds by saying that yes, in Ackerman’s thought experiment, we know justice calls out for equality, and we know what it means to treat people equally there.

However, Schmidtz says, the thought experiment doesn’t do the work Ackerman tries to make it do. Ackerman thinks the thought experiment usefully models our real situation. Schmidtz disagrees and says, what if we complicate the story a bit? What if we don’t arrive at the apple tree simultaneously? What if Schmidtz gets there 50 years ahead of time and turns the apple tree into an orchard with lots of apples. If Ackerman shows up 50 years after Schmidtz has been working, it’s not at all obvious what claim, if any, Ackerman has to the apples. It’s not clear that justice calls out for equality in this situation, and it’s not clear what it would mean to treat people equally there.

Ackerman has another thought experiment: Imagine we are all stuck on a spaceship, looking for a world to colonize. We come across an earth-like planet filled with resources. He asks, how should we distribute those resources? Schmidtz says that this may be a case where justice calls for equality, and we know what it would mean to treat people equally here. But what if we complicate the story somewhat? What if the world we find is already inhabited and the resources are already being used? It’s not clear that justice cries out for equality in this situation, and it’s not clear what it would mean to treat people equally.

Schmidtz does say that his versions of the thought experiments are a bit closer to the real world than the Ackerman’s versions. But he doesn’t say that the real world is exactly like his versions of the thought experiments, either. So, Schmidtz would never say that his versions of the thought experiments definitely proves his theory of justice (a liberal theory he somewhat joking calls “tectonic functionalism”) is true. His point is just that justice won’t allow us to treat all the stuff in the world as unowned manna from heaven, upon which no one has any prior moral claim. Despite knowing better, many philosophers and laypeople are apt to do this.

So that short video segment wasn’t meant to tell anyone the whole truth about justice. It was to simply to display some insight, and say that the whole truth, whatever that is, will contain this insight.

When reading any blog, not just this one, it’s worth taking people on their terms. When discussing anything with anyone, it’s worth just taking that person on her terms. If you suspect a person might use an insight as a premise in a second argument, an argument that will have a conclusion you dislike, there’s a strong temptation to deny or trivialize the insight, to immediately start bashing the conclusion of the second argument (the argument the person didn’t yet make), and so on. Good critical thinking demands that we not succumb to this temptation.