Practice
Practice
Five real philosophical arguments to map in Because. Work each one out for yourself, then compare with the model solution.
Reading about argument maps only gets you so far. Pick an argument below, open it in Because, and map it. Copy the passage into a claim box, break it into its reasons and objections, and make the reasoning visible enough to argue about. When you’re happy with your map, run the quick checks under the argument, then open the model solution and see where you agree — and where you don’t. Disagreeing with the model solution, and working out why, is where a lot of the learning happens.
Are you a brain in a vat?
Excerpted by Adam Elga, with minor changes, from Michael Huemer’s “Epistemology: contemporary readings.”
Read the passage
All of your brain’s information about the world comes from electrical impulses that your sense organs and nerves send to your brain. Now, imagine the following scenario. Scientists in a technologically advanced society have figured out how to keep a brain alive, floating in a vat. They have also developed technology for directly stimulating a brain electrically in order to produce a complete set of experiences as of normal life. So why should you believe that this scenario is not actually true, and that you are not, right now, a brain in a vat?
You shouldn’t. That’s because all the evidence you have for or against claims about the external world comes from your sensory experiences. But in the brain-in-a-vat scenario, you would be having the same sort of sensory experiences you are in fact having. So your actual sensory experiences are not evidence against the brain-in-a-vat scenario. So you have no evidence that you are not a brain in a vat. So you shouldn’t believe that you are not a brain in a vat.
Mapped it? Check your work.
Step 1 · The top box
Every other claim in the passage is working for one of these. Which goes in the top box?
Show the answer
Answer: You should not believe that you are not a brain in a vat.. Right. Everything else in the passage is working for that final "shouldn’t believe" — including the no-evidence claim, which is a stop along the way, not the destination.
Step 2 · The hidden premise
The argument needs the principle "you shouldn’t believe a claim is false unless you have some evidence against it." Is that principle stated in the passage?
Show the answer
Answer: No — it’s an unstated assumption. Dashed-border territory.. Right — the author never says it. The argument needs it to get from "no evidence" to "don’t believe," so in the map it gets a dashed border. Sniffing out claims like this is most of the sport.
Show the model solution
Conclusion (1.1): ‘You should not believe you are not a brain in a vat (BIV).’. It is supported by one reason. A reason supports the conclusion, containing claims 2.1 (implicit) ‘You shouldn’t believe that a claim is false unless you have some evidence against it.’ and 2.2 ‘You have no evidence against the claim that you are a BIV.’. A reason supports claim 2.2, containing claims 3.1 ‘Your sensory experience does not provide evidence against the claim that you are a BIV.’, 3.2 ‘All of your evidence concerning the external world comes from your sensory experience.’, and 3.3 (implicit) ‘The claim that you are a BIV is a claim about the external world.’. A reason supports claim 3.1, containing claims 4.1 ‘Your sensory experience is the same in the BIV scenario as it is in the normal-human scenario.’ and 4.2 (implicit) ‘When your sensory experience is the same in each of two scenarios, that experience is not evidence against either scenario.’.
From the margin notes: the dashed evidence principle is contested territory — see the Stanford Encyclopedia’s entry on Evidentialism; and on whether all your evidence really comes from sensory experience, see Rationalism vs. Empiricism.
Vegetarianism
Read the passage
Do you think your local butcher will reduce the amount of meat she orders from the slaughterhouse if you become a vegetarian? Of course not! The supply chain for meat just isn’t sensitive to the quantities that a single person consumes. So by becoming a vegetarian, you’ll never save a single animal’s life! But by becoming a vegetarian you’ll deprive yourself of the pleasure of eating meat, and you should only do that if the benefits would outweigh the losses. So you should only become a vegetarian if doing so would save some animals’ lives.
Mapped it? Check your work.
Step 1 · The top box
What goes in the top box?
Show the answer
Answer: You shouldn’t become a vegetarian.. Right — and notice the passage never quite says it. It hands you "you should only become a vegetarian if…" and "you’ll never save a single animal’s life" and trusts you to put them together. The top box is where they land.
Step 2 · The shape
"You should only become a vegetarian if there’s a decent chance of saving animals’ lives" and "the chances are minuscule" — one bracket or two?
Show the answer
Answer: One bracket: they support the conclusion only as a team.. Right — run the falsity test: if the chances weren’t minuscule, the "only if" claim would sit there doing nothing, and vice versa. They lift together or not at all.
Show the model solution
Conclusion (1.1): ‘You shouldn’t become a vegetarian’. It is supported by one reason. A reason supports the conclusion, containing claims 2.1 ‘You should only become a vegetarian if there’s a decent chance that by doing so you will save animals’ lives.’ and 2.2 ‘The chances of you saving animals’ lives by becoming a vegetarian are minuscule.’. A reason supports claim 2.1, containing claims 3.1 ‘By becoming a vegetarian you will lose the pleasure of eating meat.’, 3.2 ‘You should only deprive yourself of pleasure if there is a decent chance of the benefits outweighing the losses.’, and 3.3 (implicit) ‘The only relevant benefit of becoming vegetarian is the potential to save animals’ lives.’. A reason supports claim 2.2, containing claims 3.4 ‘The supply chain is not sensitive to the quantities of meat that a single person consumes.’ and 3.5 (implicit) ‘The only way that your becoming a vegetarian could save animals’ lives is by influencing the supply chain.’.
The model’s own challenge: can you figure out what’s wrong with this argument? (The Hints page picks this very argument apart at the end — but have a real go first.)
Biological immortality
Read the passage
People often tell me that a good life is supposed to end in old age, but I disagree. I think we have a moral duty to eradicate great evils, so I think we have a moral duty to eradicate aging. Consider an imaginary illness called “HIV/SCHMAIDS.” SCHMAIDS is like HIV/AIDS, except at just the point when a person would die from AIDS, they’d spontaneously recover from SCHMAIDS. Now, of course AIDS is way worse than SCHMAIDS. SCHMAIDS, even if it were real, would not be the great evil that AIDS is. So it is really death that is the great evil. But the number of deaths caused by AIDS is tiny compared to the unimaginable carnage of aging: in just two weeks, aging kills around 1.5 million people—more people than AIDS kills in an entire year! Aging is the major cause of death on earth. So aging, too, is a great evil.
Mapped it? Check your work.
Step 1 · The top box
What goes in the top box?
Show the answer
Answer: We have a moral duty to eradicate aging.. Right — the SCHMAIDS business, the carnage statistics, all of it is in service of that duty claim. "Aging is a great evil" is the argument’s biggest way-station, but it’s still a way-station.
Step 2 · The thought experiment
What job does the SCHMAIDS story do?
Show the answer
Answer: It’s the argument for "death is a great evil": AIDS is a great evil, SCHMAIDS isn’t, and the only difference is death.. Right. The only difference between AIDS and SCHMAIDS is death, and only one of them is a great evil — so death must be what makes the difference. That’s a real reason, not stage-setting.
Show the model solution
Conclusion (1.1): ‘We have a moral duty to eradicate aging.’. It is supported by one reason. A reason supports the conclusion, containing claims 2.1 ‘Aging is a great evil.’ and 2.2 ‘We have a moral duty to eradicate great evils.’. A reason supports claim 2.1, containing claims 3.1 ‘Death is a great evil.’ and 3.2 ‘Aging is the major cause of death.’. A reason supports claim 3.1, containing claims 4.1 ‘SCHMAIDS is not a great evil.’, 4.2 ‘AIDS is a great evil.’, and 4.3 ‘The only difference between AIDS and SCHMAIDS is that AIDS causes death.’.
From the margin notes: you could add an implicit claim like “things that cause great evils are themselves great evils” under the aging step. Simon finds it unnecessary — do you?
Argument from Illusion
Read the passage
Look around you. What do you see? Perhaps you’ll say, “Well, I see the world, of course! The desk; the computer; my partner. What could be clearer?” However, consider that when you look at a straight stick half submerged in water, an optical illusion leads you to see something bent. Now remember, the actual physical stick is straight. The only bent thing for you to see is something mental—a mental image of the stick. And as there isn’t any difference in the kind of thing you see in the case of an optical illusion and in normal perception, this demonstrates that in normal visual perception, instead of seeing physical objects, you actually only see your own mental images!
Mapped it? Check your work.
Step 1 · The top box
What goes in the top box?
Show the answer
Answer: In normal visual perception, you only see your own mental images.. Right — the illusion case is the ladder; the startling claim about normal perception is where the argument is climbing.
Step 2 · Digging deeper
In the illusion case, why believe "you see something bent" at all?
Show the answer
Answer: It rests on "it looks bent" plus an unstated bridge: if it looks like there’s a bent thing, you’re seeing a bent thing.. Right — and that unstated bridge is where philosophers pile in. (The model’s margin notes point you to Disjunctivism and Adverbialism if you want to join the fight.)
Show the model solution
Conclusion (1.1): ‘In normal visual perception, you only see your own mental images.’. It is supported by one reason. A reason supports the conclusion, containing claims 2.1 ‘You see the same kind of thing in normal perception as you see in the visual illusion case.’ and 2.2 (implicit) ‘In the visual illusion case, what you see is a mental image.’. A reason supports claim 2.2, containing claims 3.1 ‘You see something bent.’ and 3.2 ‘The only bent thing for you to see is a mental image of the stick.’. A reason supports claim 3.1, containing claims 4.1 (implicit) ‘You see something that looks bent.’ and 4.2 (implicit) ‘If it looks to you like there is something with some property, then you are seeing something with that property.’.
From the margin notes: the whole subtree under the illusion claim should be read as beginning “In the visual illusion case…”. Philosophers who reject the same-kind-of-thing claim are known as Disjunctivists; the theory that rejects the looks-like bridge principle is called Adverbialism. And the bent-stick reason wasn’t in the passage — Simon supplies it just for your interest.
Fatalism
Created by Adam Elga for Princeton FRS 105, 2013.
Read the passage
Relax! Why are you so worried about that air-raid siren? Look, either there’s a bomb out there with your name on it, or not. If there is, nothing you do will stop it from getting you: going to the air-raid shelter won’t help, praying won’t help, staying out of the open won’t help. That’s just common sense. And if there’s no bomb out there with your name on it, then you might as well relax and enjoy the sunshine out here in the plaza. Everyone knows that what you do can’t save your life. Think of it this way. Imagine looking at video tapes of all of the people who died from bombs. None of the measures they took made any difference---even the ones who headed for shelters still got zapped. Now watch the video tapes of all of the people who didn’t die from bombs. Nothing they did harmed them---the ones who just sat back and relaxed ended up as alive as the ones who ran around and worried. So stop being an idiot running around looking for the air-raid shelter.
Mapped it? Check your work.
Step 1 · The top box
What goes in the top box?
Show the answer
Answer: You shouldn’t seek shelter to avoid being bombed.. Right — the dilemma machinery all serves that practical "don’t bother" at the top.
Step 2 · Finding the flaw
This argument is no good. Where does it break?
Show the answer
Answer: The unstated claims inside each horn — like "failure to seek shelter by those who were bombed has in no case caused them to be bombed" — are false.. Right — the model stamps both implicit claims with a note: this implicit claim is false! People who got bombed often would have been fine had they sought shelter. The either/or is harmless; the smuggled premises do the damage.
Show the model solution
Conclusion (1.1): ‘You shouldn’t seek shelter to avoid being bombed.’. It is supported by one reason. A reason supports the conclusion, containing claims 2.1 ‘Seeking shelter would take work.’, 2.2 ‘Whether you seek shelter won’t make a difference to whether you are bombed.’, and 2.3 (implicit) ‘You shouldn’t work to avoid being bombed unless doing so will make a difference to whether you are bombed.’. A reason supports claim 2.2, containing claims 3.1 ‘Either you will be bombed or you won’t.’, 3.2 ‘If you will be bombed, seeking shelter won’t make a difference to whether you are bombed.’, and 3.3 ‘If you won’t be bombed, seeking shelter won’t make a difference to whether you are bombed.’. A reason supports claim 3.2, containing claims 4.1 ‘Shelter-seeking by those who have been bombed has in no case prevented them from being bombed.’ and 4.2 (implicit) ‘Failure to seek shelter by those who have been bombed has in no case caused them to be bombed.’. A reason supports claim 3.3, containing claims 4.3 ‘Failure to seek shelter by those who are not bombed has in no case caused them to be bombed.’ and 4.4 (implicit) ‘Shelter-seeking by those who are not bombed has in no case prevented them from being bombed.’.
From the margin notes: both dashed claims get a stamp in the model — this implicit claim is false! People who were bombed often would have been fine had they sought shelter. The either/or is harmless; the smuggled premises do the damage.
Course assignments#
Want more? The full set of graded exercises from my course, “A Visual Intro to Philosophy,” is available online, ordered from easier to harder. Copy each argument into Because, map it yourself, and use the accompanying materials to check your work.