The true nature of art, existence, and intelligence are all substantial topics - highly substantial! In each case, like the physical house-on-fire, there is an object of inquiry independent of the name we give it.
With respect to art - think of the analogous question concerning science. Would you be so quick to claim that whether something is science is purely a matter of definition?
With respect to existence - whether the universe is real - we can distinguish possibilities such as: there really is a universe containing billions of light-years of galaxies full of stars; there is a brain in a vat being fed illusory stimuli, with the real world actually being quite unlike the world described by known physics and astronomy; and even solipsistic metaphysical idealism - there is no matter at all, just a perceiving consciousness having experiences.
If I ponder whether the universe is real, I am trying to choose between these and other options. Since I know that the universe appears to be there, I also know that any viable scenario must contain "apparent universe" as an entity. To insist that the reality of the universe is just a matter of definition, you must say that "apparent universe" in all its forms is potentially worthy of the name "actual universe". That's certainly not true to what I would mean by "real". If I ask whether the Andromeda galaxy is real, I mean whether there really is a vast tract of space populated with trillions of stars, etc. A data structure providing a small part of the cosmic backdrop in a simulated experience would not count.
With respect to intelligence - I think the root of the problem here is that you think you already know what intelligence in humans is - that it is fundamentally just computation - and that the boundary between smart computation and dumb computation is obviously arbitrary. It's like thinking of a cloud as "water vapor". Water vapor can congregate on a continuum of scales from invisibly small to kilometers in size, and a cloud is just a fuzzy naive category employed by humans for the water vapor they can see in the sky.
Intelligence, so the argument goes, is similarly a fuzzy naive category employed by humans for the computation they can see in human behavior. There would be some truth to that analysis of the concept... except that, in the longer run, we may find ourselves wanting to say that certain highly specific refinements of the original concept are the only reasonable ways of making it precise. Intelligence implies something like sophisticated insight; so it can't apply to anything too simple (like a thermostat), and it can't apply to algorithms that work through brute force.
And then there is the whole question of consciousness and its role in human intelligence. We may end up wishing to say that there is a fundamental distinction between conscious intelligence - sophisticated cognition which employs genuine insight, i.e. conscious insight, conscious awareness of salient facts and relations - and unconscious intelligence - where the "insight" is really a matter of computational efficiency. The topic of intelligence is the one where I would come closest to endorsing your semantic relativism, but that's only because in this case, the "independent object of inquiry" appears to include heterogeneous phenomena (e.g. sophisticated conscious cognition, sophisticated unconscious cognition, sophisticated general problem-solving algorithms), and how we end up designating those phenomena once we obtain a mature understanding of their nature, might be somewhat contingent after all.
Part of the sequence: Rationality and Philosophy
Thomas Kelly
Jason Brennan
After millennia of debate, philosophers remain heavily divided on many core issues. According to the largest-ever survey of philosophers, they're split 25-24-18 on deontology / consequentialism / virtue ethics, 35-27 on empiricism vs. rationalism, and 57-27 on physicalism vs. non-physicalism.
Sometimes, they are even divided on psychological questions that psychologists have already answered: Philosophers are split evenly on the question of whether it's possible to make a moral judgment without being motivated to abide by that judgment, even though we already know that this is possible for some people with damage to their brain's reward system, for example many Parkinson's patients, and patients with damage to the ventromedial frontal cortex (Schroeder et al. 2012).1
Why are physicists, biologists, and psychologists more prone to reach consensus than philosophers?2 One standard story is that "the method of science is to amass such an enormous mountain of evidence that... scientists cannot ignore it." Hence, religionists might still argue that Earth is flat or that evolutionary theory and the Big Bang theory are "lies from the pit of hell," and philosophers might still be divided about whether somebody can make a moral judgment they aren't themselves motivated by, but scientists have reached consensus about such things.
In its dependence on masses of evidence and definitive experiments, science doesn't trust your rationality:
Sometimes, you can answer philosophical questions with mountains of evidence, as with the example of moral motivation given above. But or many philosophical problems, overwhelming evidence simply isn't available. Or maybe you can't afford to wait a decade for definitive experiments to be done. Thus, "if you would rather not waste ten years trying to prove the wrong theory," or if you'd like to get the right answer without overwhelming evidence, "you'll need to [tackle] the vastly more difficult problem: listening to evidence that doesn't shout in your ear."
This is why philosophers need rationality training even more desperately than scientists do. Philosophy asks you to get the right answer without evidence that shouts in your ear. The less evidence you have, or the harder it is to interpret, the more rationality you need to get the right answer. (As likelihood ratios get smaller, your priors need to be better and your updates more accurate.)
Because it tackles so many questions that can't be answered by masses of evidence or definitive experiments, philosophy needs to trust your rationality even though it shouldn't: we generally are as "stupid and self-deceiving" as science assumes we are. We're "predictably irrational" and all that.
But hey! Maybe philosophers are prepared for this. Since philosophy is so much more demanding of one's rationality, perhaps the field has built top-notch rationality training into the standard philosophy curriculum?
Alas, it doesn't seem so. I don't see much Kahneman & Tversky in philosophy syllabi — just light-weight "critical thinking" classes and lists of informal fallacies. But even classes in human bias might not improve things much due to the sophistication effect: someone with a sophisticated knowledge of fallacies and biases might just have more ammunition with which to attack views they don't like. So what's really needed is regular habits training for genuine curiosity, motivated cognition mitigation, and so on.
(Imagine a world in which Frank Jackson's famous reversal on the knowledge argument wasn't news — because established philosophers changed their minds all the time. Imagine a world in which philosophers were fine-tuned enough to reach consensus on 10 bits of evidence rather than 1,000.)
We might also ask: How well do philosophers perform on standard tests of rationality, for example Frederick (2005)'s CRT? Livengood et al. (2010) found, via an internet survey, that subjects with graduate-level philosophy training had a mean CRT score of 1.32. (The best possible score is 3.)
A score of 1.32 isn't radically different from the mean CRT scores found for psychology undergraduates (1.5), financial planners (1.76), Florida Circuit Court judges (1.23), Princeton Undergraduates (1.63), and people who happened to be sitting along the Charles River during a July 4th fireworks display (1.53). It is also noticeably lower than the mean CRT scores found for MIT students (2.18) and for attendees to a LessWrong.com meetup group (2.69).
Moreover, several studies show that philosophers are just as prone to particular biases as laypeople (Schulz et al. 2011; Tobia et al. 2012), for example order effects in moral judgment (Schwitzgebel & Cushman 2012).
People are typically excited about the Center for Applied Rationality because it teaches thinking skills that can improve one's happiness and effectiveness. That excites me, too. But I hope that in the long run CFAR will also help produce better philosophers, because it looks to me like we need top-notch philosophical work to secure a desirable future for humanity.3
Next post: Train Philosophers with Pearl and Kahneman, not Plato and Kant
Previous post: Intuitions Aren't Shared That Way
Notes
1 Clearly, many philosophers have advanced versions of motivational internalism that are directly contradicted by these results from psychology. However, we don't know exactly which version of motivational internalism is defended by each survey participant who said they "accept" or "lean toward" motivational internalism. Perhaps many of them defend weakened versions of motivational internalism, such as those discussed in section 3.1 of May (forthcoming).
2 Mathematicians reach even stronger consensus than physicists, but they don't appeal to what is usually thought of as "mountains of evidence." What's going on, there? Mathematicians and philosophers almost always agree about whether a proof or an argument is valid, given a particular formal system. The difference is that a mathematician's premises consist in axioms and in theorems already strongly proven, whereas a philosopher's premises consist in substantive claims about the world for which the evidence given is often very weak (e.g. that philosopher's intuitions).
3 Bostrom (2000); Yudkowsky (2008); Muehlhauser (2011).