The “Knee Defender” is a small device that airline passengers attach to the seat of front of them to prevent it from reclining. Recently, one passenger used the device on a United Airlines flight from Newark to Denver. The passenger whose seat was disabled objected, a fight ensued, and the flight had to be diverted to Chicago where both passengers were booted off the plane.

Is using the Knee Defender unethical? Should airlines prohibit it? Justin Weinberg challenges philosophers to use their analytical toolkit to think about the situation. Here’s my take.

Who Has the Property Rights? – When you purchase an airline ticket, part of what you are purchasing is a kind of limited property right in your seat. Some of the implications of that property right are clear. You have the right to prevent others from sitting in your seat without your consent. You have the right to allow others to sit in your seat with your consent. But the emergence of the Knee Defender reveals a case in which the relevant property rights are somewhat less than clear. Is the right to recline without interference part of what you purchase when you buy your ticket? Or does the passenger behind you have a property right in his personal space that your reclining would violate? Airlines have yet to establish clear rules on this matter, so at present the question can only be answered by investigating into what we might call conventional property rights – property rights that exist as a matter of informal social practice rather than formal legal or corporate rules. Conventional rights are sometimes difficult to ascertain, which is why some (like Damon Darlin) are able to assert confidently that use of the Knee Defender is within a passenger’s rights, while others (like Josh Barro) view its use as a kind of “theft.” My own reading of the convention is in line with Barro’s. Airlines buy planes with seats that recline because they want customers to be able to lean back, just like they make seats with televisions in them because they want customers to be able to watch them. If you’re bothered by passengers around you watching television or leaning back, you’re free to ask them to stop. But you’re not free to forcibly prevent them by disabling their television or their seat.

Who Should Have the Property Rights? – Even if property rights were clearly defined, though, we could still meaningfully ask whether they’ve been defined well. Maybe things would be better – more fair, more efficient – if people didn’t have the right to recline. Suppose everybody likes to recline, but they really like not to be reclined upon. In that case, they might have a preference ranking that looks something like the following:

1. I lean back; the person in front of me does not.
2. I don’t lean back; the person in front of me doesn’t lean back.
3. I lean back; the person in front of me leans back.
4. I don’t lean back; the person in front of me does.

The best situation, from your perspective, is one in which you recline but are not reclined upon. But if most people share your preferences, this is unlikely to occur. After all, others like to recline too. More likely is outcome (3). But outcome (3) is worse, on your preference ranking, than outcome (2). You could try to move from (3) to (2) by talking to the people in front of and behind you, and maybe trying to strike up some kind of deal. But if enough people share your preferences, maybe it would just be simpler if the airlines changed their rules so as to disallow reclining in the first place. (It’s just like a prisoner’s dilemma, where Reclining = Defecting and Not Reclining = Cooperating. Even though we all might prefer to defect while others cooperate, the best institutional solution might be to prohibit defection altogether)

Better still, rather than barring reclining outright, they could simply assign the property right to the person sitting behind the recliner. That person would “own” their space, and could prevent you from reclining by withholding their consent. But if you wanted to recline much more than they wanted you not to recline, you could always pay them. It’s the Coase Theorem in action. Regardless of  how the property rights are initially allocated, as long as people are free to transact at relatively low cost, the right will tend to wind up with whoever values it more anyway.

Efficiency isn’t the only consideration relevant to determining how property rights ought to be allocated. We care about fairness, too. So, for instance, some people think that even if a market in human kidneys would be efficient, it would be unfair insofar as the wealthy would benefit from such a market at the expense of the poor. I think that critique is misguided, but you see the concern.

I can’t see how anything like that is relevant to the Knee Defender case though. People who are flying on airlines are not, as a rule, desperately poor. And the cost of being unable to afford to purchase the right from the person in front of or behind you is mild inconvenience, not death or long-term dialysis. So I’m hard pressed to think of any serious fairness considerations that could overcome the efficiency argument for allowing a market to emerge.

Here’s a different kind of worry though. Suppose we go with Baro’s proposal. You as a ticket holder have the right to recline, and if the people behind you don’t like it, they can offer to pay you to stop. What kind of incentives does that create? Well, suppose I’m the kind of person who doesn’t want to recline. But I do like money. So now I have an incentive to lean my seat back just to get you to pay me to stop. This looks an awful lot like what Robert Nozick described as an “unproductive exchange.”  And, like blackmail, there might be reason to prohibit this kind of exchange simply in order to prevent the kind of deadweight loss it involves.

How Should Property Rights Be Used? – I’ll close with what I hope is an obvious point: just because you have a right to do something doesn’t mean it’s the right thing to do. If I own a cabin in the woods, and you’re a lost hiker knocking at my door seeking shelter from a snowstorm, I have the right to turn you away. (Well, maybe). But doing so would be an awful thing to do. Similarly, if you’re a passenger on a plane and you see that the person seated behind you is a parent struggling to pacify a child in his lap, it would be, at the very least, highly discourteous of you to lean your seat back anyway. To have a property right in something is simply to have the ability to make enforceable claims on that thing, should one choose to do so. But just because you have the ability doesn’t mean you should exercise it.