I got into an argument with a structural engineer the other day. I was saying that it would be really cool if the Navy had something like the Helicarrier used by SHIELD in the Avengers movie. He was trying to say that it “wouldn’t work” for some kind of technical reasons, like there’s no known power source that could make something that big hover and also be on the thing, and that even if we had one, the blast from the turbines would be so powerful that it would destroy any buildings it happened to fly over. But I replied that this was just his opinion. In my opinion, it would be terrific, and these “technical” objections really shouldn’t override how awesome it would be to have a Helicarrier. He kept insisting that, unlike me, he had spent years studying physics and electromagnetism, and that therefore his “opinion” as to what was or wasn’t technically feasible was better justified than mine, and that my aesthetic preferences really didn’t amount to much in the absence of good reasons. I replied that he doesn’t have perfect knowledge, so my opinion should count just as much, and I reiterated how great it would be: it would greatly enhance naval effectiveness and air superiority, plus it would super-cool so we should just do it and make it work. Who’s to say we couldn’t possibly make it work? He kept going back to the theme that I’m not really qualified to say what would work, whereas he actually was an expert on these things. He said he realized it sounded arrogant when he put it that way, which he didn’t intend, but that he did actually have a PhD from Cal Tech, and that he was only bringing it up to help motivate the point that I didn’t have a rational basis for arguing with him about this.
The above anecdote is fictional, of course, yet it’s analogous to the kinds of arguments economists and political philosophers often find themselves in. The word “rights” can’t just mean whatever you want it to mean, and not every conception of rights will be coherent. In a democratic society, everyone is entitled to have their voice heard, but it’s a mistake to infer from this that everything is up for grabs, that Locke and Marx (or Keynes and Hayek) are “just different opinions.”