The Problem of Knowing Others’ Mental States
I think that others, including both humans and non-human animals, have mental states. I think certain things about their mental states, for example, that some, but not all, people perceive colors. But do I have any reason to believe any of this? My knowledge of others’ mental states seem to be private. That is, I cannot have any direct access to others’ mental states. I can only have direct access to my own mental states. So how can I justify my beliefs about others’ mental states, including my belief that others have mental states? If I cannot justify my beliefs about others’ mental states, then it’s not clear how I can know anything about others’ mental states. This is a problem, what I refer to as the problem of knowing other’s mental states.
If I cannot know anything about others’ mental states, then I cannot know if I’m giving pleasure or causing pain to others. If that’s the case, it’s not clear that I would be doing something immoral if I treat you like an object, something I can manipulate for my own pleasure. It’s not clear why I should spend any time worrying about the mental well-being of others, since I cannot know if anyone else suffers. In a later post, we will examine more closely the relationship between mental states and value.
Underlying this problem of knowing about other’s mental states is the idea that I can conceive of others behaving as I do in similar situations but these same others having different mental states than I have or no mental states at all. Consider the following case. I am outside in a park with my friend and we are both looking at some patch of grass. My friend and I, who both use color terms the same way, agree that the grass is green. Isn’t it conceivable that when my friend looks at the grass and says it looks green, the way the color of the grass looks to him is the way red things look to me? Isn’t it conceivable that the color of the grass doesn’t look any way at all to my friend? Couldn’t he be like a machine that can identify colors, but doesn’t have any conscious perception of them? As you think about these questions (assuming you can think), keep in mind that the scenario asserts that my behavior and my friend’s behavior are the same. So it’s not that my friend is colorblind and says that he is seeing no colors or a different color. Rather, he claims to be perceiving the colors the same way that I’m perceiving them. Since I seem to be able to conceive of these things, the skeptic argues I need to be able to show that they are not actually the case in order to know anything about the perception of my friend. But how can I show this, given that I cannot directly access his mental states?
According to the skeptic, it’s not only the perception of colors in others that I cannot know anything about. The skeptic argues that I can’t know anything about the mental states of others. Here is how the skeptic argues for this radical claim:
- It’s conceivable that others behave as I do in similar circumstances but have different kinds of mental states or have no mental states at all.
- The only way I can know anything about the mental states of others is by making an inference – i.e. drawing a conclusion – based on how others look – their physical makeup – and how they behave in certain circumstances.
- But there is no way for me to know whether such an inference is any good.
- Therefore I cannot know anything about the mental states of others, even if they have any.
Before we examine some responses to this skeptical argument, I want to emphasize that the skeptic is not claiming that others do not have mental states. Nor is the skeptic claiming that others mental states are in no way to similar to or different from my mental states. What the skeptic is claiming is that I cannot know anything about the mental states of others. So if others do have mental states or their mental states are similar to or different from mine, then, according to the skeptic, I cannot know this. Since I think the skeptic is mistaken, I need to respond to his argument.