Last time, we left off saying there’s a group of arguments for dualism where the premises do all seem to be plausible, even to people who haven’t yet subscribed to dualism. And it’s not obvious that any words need to switch their meaning halfway through the argument, for the premises to seem obvious in this way.
The general flavor of these arguments can be summarized like this:
The specifics of these arguments will turn on how they unpack the notion of this “special access.”
Here are some things philosophers say to explain what they mean here:
The details are controversial: for example, some philosophers think you can’t make mistakes about the properties of your own mind. If you have a headache you’ll know you do and it won’t be possible for you to think you have one when you don’t. Other philosophers think you can make mistakes about at least some of your mind’s properties. You might think you’re happy for your friend’s success (and not envious), but in fact you’re envious (and not happy about it).
It’s enough for the purposes of this class just to know that there are some controversies here, especially concerning the first claim. But if you want to read more, here are some notes from another course:
See also the page on intensions that I mention below.
Despite those controversies, many philosophers would agree that our access to (at least some parts or aspects of) our own minds is “special” in one or more of the ways listed. (Especially the second and third way.) And we don’t seem to have that same special access to anyone else’s mind, nor to facts about our brains or bodies or things in our physical environments.
Perhaps this can be used in an argument by Leibniz’s Law that our minds aren’t identical to anything physical.
For example:
Here’s the argument that van Inwagen discusses, unpacking “specialness” in our sense (c):
As above, “intelligibly doubting” something here means roughly to imagine it not existing even though everything seems the same.
These applications of Leibniz’s Law are more challenging than the ones we considered before. It’s less clear how the materialist should respond here. What do you think?
How should the materialist respond to these arguments?
Let’s consider a different example. Suppose Lex Luthor thinks he has succeeded in destroying Superman. In fact, Superman is alive and well, and is walking on the street below, dressed as Clark Kent.
Lex argues:
All of the premises of this argument seem plausible. Yet its conclusion is false. Superman is one and the same person as the reporter Lex sees. So this argument seems to be invalid. Something about the reasoning here must be broken.
Here’s another example.
Note that the argument here is not about the property is in fact wearing a gray suit. If Lex ascribed that property to the reporter but denied it to Superman, he’d just be making a mistake. One of his premises — that Superman is not wearing a gray suit — would just, unbeknownst to him, be false. That would be like our use of Leibniz’s Law to argue that the butler is not the murderer, when the butler has tricked me into accepting the false premise that he’s not left-handed. The argument we’re considering now is supposed to be different. Here the property that the reporter and Superman are supposed to differ with respect to is not wearing a gray suit, but rather being thought by Lex to be wearing a gray suit. Even if Superman and the reporter Clark Kent are the same person, doesn’t it still seem right to say that Lex thinks that Clark is wearing a gray suit, but doesn’t think that Superman is wearing a gray suit? So here there is more intuitive pressure to say that both premises of the argument are really true. Here it looks like the reporter does have some property that Superman lacks! Even though, as we set the story up, the reporter is in fact just Superman in disguise.
Apparently, Leibniz’s Law is broken when we’re dealing with cases of this sort. This kind of reasoning, that has to do with what people think, or have evidence for believing, or doubt, and so on — cases that seem to essentially involve people’s perspective on things — doesn’t seem like a place where Leibniz’s Law can be validly applied.
It may be useful to know that philosophers use the label intensional language for cases of this sort. There’s also another word philosophers use, “intentional” (with a t instead of an s) that has a connected meaning, but these aren’t exactly the same.
Philosophers sometime use "intentional" to mean something like "representational."You don’t need to master this vocabulary in this course, but here are some notes on intensions if you want to read more about it.
Here’s another example. Lex says:
Again, the premises seem true but the conclusion is false. This is another invalid application of Leibniz’s Law.
Other examples might use premises about being famous, or whether Lois hopes that he’ll kiss her, and so on.
There are big debates in contemporary philosophy about how we should explain these breakdowns of Leibniz’s Law. One strategy is to deny that being thought by me to be wearing a gray suit and the like are genuine properties. This is the strategy van Inwagen takes when discussing these kinds of arguments. But other philosophers prefer different explanations. If you take more advanced classes in philosophy of mind or philosophy of language, you will definitely spend time studying those debates. All you need to know for now is that Leibniz’s Law does break down in some way when you’re dealing with these kinds of cases.
Now the arguments for dualism we were looking at at the top of this webpage seem to be of this problematic sort.
One of them had to do with when something’s existence can be doubted, just like the first of the clearly invalid arguments presented by Lex Luthor. Another had to do with the kind of access people have to their own minds versus physical objects. But that’s a matter of what kind of evidence and reasons they have for thinking things. It seems problematic to use considerations like that in Leibniz’s Law arguments too. After all, Lex would be making a mistake if he reasoned:
In response to the kinds of Leibniz’s-Law-based arguments for dualism we’ve seen so far, a materialist/physicalist would make one (or more) of these objections:
The dualist may be equivocating, instead of using notions in a single consistent way for her whole argument.
The dualist may be begging the question, that is, relying on a premise that’s too controversial/disputed to help settle a debate about whether to accept dualism.
The dualist may be applying Leibniz’s Law illegitimately in ways that exploit different perspectives, as in the arguments we attributed to Lex Luthor.
As we said earlier, these Leibniz’s-Law-based arguments could anyway at best show that minds aren’t identical to a physical object/substance. But that’s not yet “the right shape” of argument to, on its own, fully establish dualism. One could agree with that conclusion, without yet accepting that minds are identical to a different kind (a non-physical, esssentially thinking) object/substance, as the dualist wants. One could still be a materialist/physicalist, while denying that minds are any kind of object/substance. They could say that minds are more like hikes or dances. What makes them a materialist is that they think all the objects there are, are physical. But they don’t have to say that the minds are some of those physical objects, anymore than we have to say that hikes or dances are.
There are other, more promising strategies the dualist might appeal to, in support of their view. In this course, we’re not going to have the time to explore those arguments, or the different philosophical issues they raise. We’ll just note that there are other strategies for arguing for dualism than the ones we’ve looked at so far, which weren’t that successful.
And look, even if the dualist weren’t able to come up with a really compelling argument for their view, the view might nonetheless still be correct. Sometimes things are true even if nobody can prove—or even if nobody knows—that they are true. So materialists shouldn’t get too pleased with themselves if all they’ve managed to do is criticize some arguments for dualism. If they want to argue for their own view, and so against dualism being true, they’d have to do more work.