Yesterday saw a revival of the so far not so fruitful debate between Jason Brennan and Ross Levatter about the thought experiment that Brennan had proposed at the BHL blog. Levatter responded to that post with harsh criticism followed by a brief dismissal by Brennan. Now Levatter has written a detailed follow-up. I cannot match Levatter in terms of breadth but I will try to capture the core of the disagreement.
From what I saw in the related discussions in the blogosphere, the reactions to Levatter’s criticism of Brennan seem to polarize. People who side with Brennan do not see much point in Levatter’s criticism thinking that he misunderstands the purpose of thought experiments like the one Brennan proposed. Those on Levatter’s side tend to be amused by the dismissive reaction of the former.
I think that the problem here runs deeper than a disagreement about soundness of a particular thought experiment. It has deep roots in the dominant paradigm of modern academic philosophy with regard to epistemology as I see it from my reading on several topics.
This dominant paradigm is a mix of nominalism and empiricism. Simplifying things, it is well reflected in Frege’s famous distinction between sense and reference. Sense is what we mean by a certain concept. Reference is something in the real world to which the concept refers. The empiricist part of this paradigm is that it is somehow possible for the mental constructs (which concepts are thought to be) to reflect the external reality by means of testing them by and updating them after controlled experiments and their substitutes, like statistics.
A corollary of this paradigm is that truth values of propositions refer to reference, not sense, and that it is possible to make logically valid inferences with the use of what are thought to be concepts that obviously do not or even may not have referents in the external world as we know it.
An example of this is a potential discussion about dragons. Dragons are imaginary beings that are supposed to have a natural ability to throw flame from their mouth. Although there are no reasons to believe that they are possible under the laws of this world, it is thought that we still can meaningfully make inferences about them. For example, we supposedly can infer that if dragons existed and if one were to throw fire at a human, a human would suffer terribly. Or if a dragon crashed into you, you would probably be crushed because a dragon presumably would have a big mass.
However, to an adherent of a competing paradigm of concepts, i.e. Aristotelian realism in my case, the above inferences are highly dubious. The key problem is that it is question-begging to assume that a world where dragons would be possible would differ from our world just in terms of the existence of dragons. Maybe mass would not exist in such a world, maybe humans would not. It should be clear by now that we cannot really meaningfully make inferences here.
The original controversial thought experiment by Brennan is, in my view, very similar to the discussions of a world with dragons because It so obviously contradicts both economic theory and the historical experience.
Thus, the core of the disagreement between Brennan and Levatter is about the philosophical treatment of possibility. The dominant modern view of possibility holds that anything is possible for the purpose of deliberation, unless its affirmation involves a logical contradiction.
The Aristotelian view which Levatter seems to consciously or unconsciously espouse, on the other hand, rejects this theory of possibility. I will conclude this post with the quote of Roderick Long putting the position very succinctly:
…but as an Aristotelean, I reject any form of possibility other than “compatibility with the nature of the actual world.” Just as explanations make sense only within the realm of existence, so the distinction between possible and impossible does so too. Thus I essentially agree with Fraçois’s answer: “Just because we can imagine the gravitational constant being, not 6.674×10^-11 m^3 kg^-1 s^-2, but rather 6.252×10^-11 m^3 kg^-1 s^-2, does not mean that it can actually be 6.252×10^-11 m^3 kg^-1 s^-2. Just because we can write it down and make calculations based on it doesn’t mean it’s actually possible.”
UPD: I should have put the word ‘straightforward’ before the words ‘logical contradiction’ in the second paragraph from the bottom because it is obvious that for example the metaphor of a being capable of throwing flame out of its mouth may be in contradiction with some fundamental feature of the actual world and the only one that we are entitled to talk about at the fundamental level from the Aristotelian standpoint. Since Aristotelian realism must reject the distinction between sense and reference (on the basis that the mind just abstracts concepts from the world), it is only meaningful to talk about a straightforward contradiction with respect to metaphors.