Perceptual Knowledge
In the 1988 film Rain Man, inspired by the autistic savant Kim Peek, Dustin Hoffman plays a character, Ray, who has unusual talents as well as unusual defects. One of his talents is that without counting he can visually ascertain the number of objects in large sets. In a memorable scene, a box of toothpicks spills on the floor of a restaurant. He looks at the spill for an instant and declares “82, 82, 82.” His brother Charlie, played by Tom Cruise, dismisses Ray, saying that there are far more than 82 toothpicks on the floor. Ray immediately responds, “A total of 246.” A waitress looks into the overturned toothpick box and observes that there are 4 toothpicks left in the box that held 250. Without counting the individual toothpicks, Ray has visually divided the spill into three groups of 82 and determined that the total is 246.
The film is constructed to suggest to viewers that Ray knows that there are three groups of 82 toothpicks on the floor. Previous scenes have drawn attention to the fact that although he has emotional problems and lacks common sense, he also has rare intellectual abilities. The cumulative effect of these scenes is to raise the salience of his unusual talents and the curious ways he deploys them. For example, early in the restaurant scene, when the waitress who later spills the toothpicks arrives at Ray and Charlie’s table, she is wearing a nametag with the name “Sally Diggs” and no other information. Ray glances at the nametag and says, “Diggs, Sally. 4610192.” The waitress is taken aback and warily asks, “How do you know my phone number?” Ray responds nonchalantly that the previous night he had memorized the local phone book through to the letter D.
This scene and others like it alert the audience that Ray has remarkable intellectual abilities, is aware of these abilities, and makes his own idiosyncratic uses of them. So, when he observes without counting that there are three sets of 82 toothpicks on the floor, it is natural for the audience to assume he has reliably made such determinations in the past and he realizes he has this ability. This assumption is corroborated when the audience sees Ray register no surprise when Sally confirms that there are in fact 246 toothpicks on the floor. He takes it for granted that he was correct.
We are sometimes reluctant to concede that someone knows P if he is unaware of how he gets information about matters such as P or lacks information about whether he has been reliable about such matters in the past.1 The scenes in Rain Man, however, are arranged to suggest that there are no gaps of this sort in Ray’s information. On the contrary, he seems as aware of and as comfortable with his ability to determine by quick visual inspection the number of objects in large sets as the rest of us are with respect to small sets (four books on the table, three people in line, two chairs in the corner).
A lack of awareness about how one acquires information or one’s track record of reliability is sometimes the kind of gap that can preclude one from knowing even if one has relatively complete information, but the reverse is also true. A working familiarity with the source of one’s belief P coupled with an awareness of the source’s reliability can sometimes help make up for a relative lack of information about P itself.
Beliefs based on testimony often display this compensatory quality. If S believes that the Yankees won last night’s game because a trusted friend who is close follower of baseball has told her so, her belief may well be an instance of knowledge even if she has relatively few details about the game. Familiarity with the reliability of a source of information about P can relax the demands for additional information about P itself.
The same dynamic is commonly at play with perceptual beliefs. The waitress comes to know by quick visual inspection that there are four toothpicks left in the box, and Ray comes to know by quick visual inspection that there are three groupings of eighty-two toothpicks on the floor. Neither Ray nor the waitress need be aware of much additional information about the toothpicks—for example, whether they are made of plastic or wood or whether they belong to the restaurant or an employee or whether they have been on the shelf for only several hours or several weeks. Additional information is especially not needed if we assume that they have a working familiarity with their histories of reliability, in the waitress’s case her history of reliability in perceptually determining the number of objects in small sets and in Ray’s case his history of reliability in perceptually determining the number of objects even in large sets.
Perceptual beliefs that are the products of cursory visual inspection are in this respect similar to memory beliefs that are the products of immediate recall. When asked the date of the Battle of Marathon, a contestant on a quiz show confidently and immediately remembers from her high school history course that the date is 490 BCE, but she cannot recall that the Greeks won the battle or even that the adversaries were the Greeks and Persians. Still, it may strike us that whatever else she does or does not know about the battle, she at least knows its date, since the story been told to focus attention on the importance of her being able to answer a specific question, what is the date of the Battle of Marathon?2 If in addition the story is constructed to suggest she has a history of reliability with respect to remembering dates and she is aware of this history, we will be all the more inclined to relax expectations about how much additional information she needs in order to know.
In a similar way, the scene of Ray in the restaurant is constructed to focus attention on a narrow question (how many toothpicks are on the floor?), and we are led to believe Ray has a working familiarity with the unusual ability that allows him to answer this question. So, as in the case of S’s remembering the date of the battle, it strikes us that whatever else he may or may not know about the toothpicks, he at least knows that there are three groups of eighty-two of them on the floor.