It seems to me that this conflates two different types of "hypothetical is unrealistic" objection. In my experience the more common and correct objection is that the hypothetical is built on a false world model, not just a scenario that won't happen for more mundane reasons.
"Should we put hazard labels on drinks if water was composed of hydrogen and chlorine instead of hydrogen and oxygen" for example.
Water is not composed of hydrogen and chlorine, and to suppose that it is requires such a huge change in very fundamental properties of the world that no answer to the question can be meaningful. There is no world sufficiently similar to our own that the question can even make sense: do the people in this world have such "water" in their bodies? What about the oceans? What about their drinks? The usual property of drinks is that they do contain water, but do they in this hypothetical?
It could be just asking "what if we swapped the terms 'water' and 'hydrochloric acid' with no actual change in the word", but that would be a pretty dumb question and also brings into question whether there are any other switcheroos, like whether the word "drinks" actually means "nuclear weapons" in there.
While that is an extreme example of what I mean, there are other hypothetical questions that are more covertly unrealistic in this sense. Even the stated example is, to some degree.
For example, if you're playing tennis on Mars, that's very likely a world that has technology substantially more advanced than ours, and it's quite plausible that in such a world people who become paralysed are able to play tennis using neural prostheses and don't suffer much incapacity at all. The supposed "universal principle" from the post has failed. It turned out that the principle was actually local to a family of possible worlds and the hypothetical went outside them.
It is unrealistic for people to play tennis on Mars, at the moment. It is also unrealistic for paralysed people to ace out decent tennis players, at the moment. Those unrealisms are correlated by the state of technological progress, so it is reasonable to object more to the "on Mars" part as being unrealistic more than to the "Christopher Walken" part. It opens up new world models that have premises that do not currently hold, and which can or will change the answer to the hypothetical.
I disagree with your characterisation that I am conflating between two different types of "hypothetical is unrealistic". I am explicitly referring to the "mere unrealism" dismissal, as opposed to dismissals based on coherence or relevance.
The "hydrogen/chlorine" water example you give is not actually testing any principle, and so it may be relevant or irrelevant, insightful/useless, depending on the principle it is testing. For instance, if you say "no matter the chemical composition of water, we shouldn't put warnings on it, because water is safe to drink", then the hypothetical question of: "what if it's made of hydrogen/chlorine instead of hydrogen/oxygen?" is actually a plausible challenge to this principle.
Your water example also potentially runs into an outright contradiction, which is acknowledged in the post as a case where it is defensible to reject it on those grounds. "Water", if defined to mean "H2O", is not merely "unrealistic", it is logically impossible for it to be "HCl", because HCl is not H2O, which is just P and not P.
For example, if you're playing tennis on Mars, that's very likely a world that has technology substantially more advanced than ours, and it's quite plausible that in such a world people who become paralysed are able to play tennis using neural prostheses and don't suffer much incapacity at all. The supposed "universal principle" from the post has failed. It turned out that the principle was actually local to a family of possible worlds and the hypothetical went outside them.
This is in complete agreement with the post. The point is that if the conclusion of the principle is false or untenable, then the principle producing it is either false or insufficiently specified. I am not literally claiming that being paralysed necessarily entails tennis-playing is off the table no matter what - I am giving it as an example of a colloquial absolute, showing that it is valid to interrogate this principle with seemingly ridiculous scenarios.
If i run into someone who refuses a hypothetical in that way, I assume they are not a serious person and stop trying to convince them. They are either playing to win the argument as opposed to being right or cannot imagine non real things. Both cases are hopeless.
1I think this is fair - if your only evidence/argument is wildly hypothetical, it's probably best to just disengage with people who don't accept the hypothetical - neither participant has points the other will take seriously. If you have other/better arguments, it may be worth discussing those.
My biggest objection is that a hypothetical is not restrained by reality. You can say "oh, but what if X?" where X is not just absurd but impossible. A general rule only has to work in all cases which can possibly be relevant at any point in time. It's unfair to expect it to hold up to any imaginary cases, even those including logic errors and contradictions - the hypothetical could even change the premises which caused the conclusion in the first place. For instance, here, I could say "What if the laws of logic didn't apply?", "What if the person who had 1 second left to live actually had 100 years?", or "What if being murdered was a blissful experience?".
The only thing which are always true are necessarily true. People do not break the laws of physics because they can't. But in the social realm, we create artifical limitations on top of those of physics.
People will say that X is right or wrong, but that's not what we actually mean by the words. These are sometimes moral terms, not mathematical ones.
Principles are something like globally optimal heuristics. The majority of murder is unjustified, and because we cannot trust one another to judge the edge cases correctly, it's optimal to say that murder is always bad. There's a value judgement here, too: "Preventing an unreasonable murder is higher value than a reasonable murder not happening".
"Murder is always wrong" is a false statement, but "it's optimal to act as if murder is always wrong" might be true under some set of environments. I dislike Kant's categorical imperative because simple general(global) rules fail in specific(local) edge cases. It's a form of tyranny, really. The no free lunch theorem makes general rules have trade-offs.
Finally, there's no universal principles, meaning, there's no principles which are not bound to a context/sphere/region. There exists universal rules, but only because the universe is something specific and finite. The mental model of an objective correctness which is unbounded is a wrong mental model. This is my own discovery, but mathematicians should already have a sense for it (that all statements have implicit restrictions like "Under set theory" or "According to current models")
My conclusion is that the title of your post isn't correct in all cases, but only in most cases. I think you put too much faith into logic and the solvability of reality.
Disagree with the genearality of this, pretty strenuously. In some specific cases you are probably right, but I expect most of those cases contain "believable" hypotheticals, where there's nothing out-of-domain for human experience.
Whenever a discussion touches ethics, philosophy, or relates to guiding principles, hypotheticals become useful.
I think this is a crux, and I think it does not generalize well. In a few cases, hypotheticals are useful to explore intuitions, or to see if boundary conditions apply. If there are no REAL examples (or at least hypotheticals that are likely to be true, even if not recorded), the whole argument is quite suspect.
Your example of tennis with Christopher Walken on Mars is believable, in the sense that it's entirely standard physics and biology. It's vanishingly unlikely, but doesn't stretch any definitions or assumptions. It's also uninteresting. Give some real examples of a disagreement where an analogy to an imaginary situation is a crux - I think you'll find that imagination is helpful in refining models and noticing inconsistency, but provides zero evidence for whether it's true in our universe.
Accepting “If X, then Y” does not require any acknowledgement of X being true or feasible.
Simply false. If X is false, then no conclusion about the truth of Y can be drawn. If X is explicitly about an alternate universe with different rules, it's MUCH harder to believe the implication of X->Y, because it'll matter WHAT SPECIFICALLY makes X true in that universe.
"[contrived case of X] is wrong" typically means "if X happens, and contrived condition happens, then X is wrong (under those circumstances)".
But a false proposition implies any proposition. If the contrived condition is not possible, then:
"if X happens, and contrived condition happens, then X is wrong" and
"if X happens, and contrived condition happens, then X is not wrong" are BOTH true, even though this seems strange.
And of course this means that "[contrived case of X] is wrong" and "[contrived case of X] is not wrong" are also both true, since they are just different ways to phrase those. Your argument assumes that they contradict. But if the contrived condition is not possible, then they don't.
Or from another angle: "[contrived case of X] is wrong" means that if Y is a member of the set "all contrived cases of X" then Y is wrong. If this set is empty, then it is simultaneously true that for all Y in that set, Y is wrong, and for all Y in that set, Y is not wrong. So "[contrived case of X] is wrong" doesn't contradict "[contrived case of X] is not wrong".
Whenever a discussion touches ethics, philosophy, or relates to guiding principles, hypotheticals become useful. We cannot investigate every idea with real experiments, but we can test the consistency and precision of principles that guide us with thought experiments. It isn’t necessary to see a man murdered in front of you to understand whether that would be good - we can simply imagine it, and realise our principles would, in that scenario, produce an answer. This process - of considering something that has not, or will not actually occur, is the basis of all counterfactual reasoning. “If X, then what?” is a piece of cognitive machinery without which we would be unable to make sense of the world.
However, it is common for people to respond to questions or statements of the form “if X, then what?”, with the maddening objection “but, not X”.
This objection is a general refusal of the word “if”
ALL hypotheticals are unrealistic - if they are realised, they cease to be hypotheticals. Being unwilling to engage in hypothetical reasoning means you are unwilling to engage in counterfactual reasoning, and are ultimately committed to exclusively considering that which has already happened or is certain to happen. By rejecting the antecedent premise of all unrealised hypotheticals, you forgo the mechanism that allows you to make plans whatsoever.
“If” inherently acknowledges that a thing does not obtain. By positing X as an “if”, you are not validly critiqued on the basis that X does not obtain. Assuming “X does not obtain” is a valid basis to dismiss a conditional premise, then this argument applies to all if statements.
One may retort by claiming the steelman principle is: “X cannot obtain”. However, this does little to alleviate the burden of engaging with contrived scenarios. For one, rejecting conditionals where X cannot obtain commits you to the view that conditionals involving the past are impossible to consider - changing the past is not physically possible. So, questions like “if you never bought a dog, would you have dog food in your house today?” are off the table.
Furthermore, even granting this “impossibility” principle, the set of things which cannot obtain is far smaller than the set of things which most likely won’t obtain. This standard requires proving some contradiction inherent in the premise, or, at a practical level, that a scenario would violate some law of physics held as an axiom.
What law of logic or physics prevents a tennis match between you and Christopher Walken?
Why “contrived” is not a valid critique of a hypothetical
A hypothetical tests a principle. If you say “murder is wrong” without qualifying the statement, you are not saying “murder is usually wrong”, or “murder is often wrong”, you are saying “for all X, if X is murder, X is wrong”. This statement, though intuitive, is, in fact, extreme and virtually indefensible without caveats[1].
The set of “all X” includes the set of “all contrived, extreme-seeming forms of X”, because those things are still X.
Consider the syllogism:
This shows that to say X is wrong (without exception), you are committed to the conclusion that all contrived and unrealistic cases of X are wrong.
So, no matter how absurd-seeming the case of X, the syllogism always holds:
Given this, you can test whether the principle of “(all) murder is wrong” holds by looking at contrived cases of murder.
1 inescapably entails 3 - therefore, if you believe that statement 3 is false, then believing 1 is true produces an outright contradiction.
Answers to absurd scenarios are necessitated by universal principles
Consider the premise:
“If I become paralysed, I will not be able to ace out any person in tennis”
If someone accepts this principle as true, per the earlier syllogism, they accept it for all cases of “any person”. Therefore, they accept they will not be able to ace out their usual tennis partners, which is obviously true.
However, this also commits them to the view that they will be unable to ace out Christopher Walken.
Further, “In tennis” does not impose a geographical constraint. So, a tennis match played on Mars would be “in tennis” by definition.
We can now put the two syllogisms together:
Therefore, by accepting premise 1, this deductively requires conditionally accepting the “unrealistic” scenario.
So, if someone says “paralysed people cannot beat anyone at tennis”, and you say “what if they played Christopher Walken on Mars?”, the only coherent answers to give are:
“yes, including Christopher Walken on Mars”; or
“No, I suppose in that case there might be a chance (perhaps Walken dies first) - therefore, the original statement is improperly specified, i.e., strictly false”
The reply: “But I would never play Christopher Walken on Mars”, is simply an irrelevant statement that fails to appreciate that 1 deductively leads to 5.
Accepting “If X, then Y” does not require any acknowledgement of X being true or feasible.
Why this objection is so common
To the untrained eye, dismissing absurd scenarios looks like rigor. A contrived thought experiment to elicit an absurd conclusion that they would never normally endorse, can come across as a sophist using a trick; a “slimy debate tactic”. This feeling of being hoodwinked comes from an almost-getting-of-the-point - realising that, indeed, if X is true, then Y would seemingly follow, and Y obviously isn’t true - so something must be awry. The explanation of “some kind of trick” is easier to reach for than the explanation that X may not be as true as you would like it to be.
Importantly, if one offers the statement of “murder is wrong” in a general sense, it is of course pointlessly pedantic to test it on contrived edge cases to see if the idea holds absolutely, since it is already understood to mean “murder is pretty much always wrong except for some really rare circumstances that I’m not talking about”. However, this dismisses the hypothetical on the basis of relevance, not on the basis of realism. So, if a pedant does challenge the “murder is wrong” premise with an edge-case hypothetical, it is still invalid to say “that edge case would never happen” - instead, the reasonable answer is “yes, not literally all murder is wrong, but we both know that, and a ten-paragraph list of qualifying statements isn’t necessary for the discussion we’re having - you know what I mean”. When the hypothetical test serves no clarifying purpose, and is merely pointing out that the wording of the premise is underspecified per a literal reading, it is a fruitless distraction. However, this “you know what I mean” response would itself only be a reasonable answer as long as the crux of the discussion isn’t contingent on the details of what exactly is meant by the statement.