General Background: The Traditional Account of Knowledge
The entries to follow begin with a bit of background information to help situate and make clear the particular puzzles, paradoxes, and thought experiments discussed. However, some general background on the traditional account of knowledge is helpful to have in hand for most all of the entries in this book. So, letâs begin by taking a brief look at how knowledge has been understood for many years.
Epistemologists have distinguished between three primary kinds of knowledge: acquaintance knowledge, knowledge-how, and propositional knowledge. Although our focus for this background, and most of the book, is the last sort, it will be helpful to take a quick look at the other two as well.
Acquaintance knowledge is knowledge you have of people and things you are familiar with personally. For example, letâs say that you have a dog, which your new acquaintance, Fred, has never seen. You tell Fred all sorts of facts about your dog. She is a Yorkshire Terrier. She is ten (human) years old. And so on. After you share this information about your dog, Fred will know a lot of facts about her. But, Fred doesnât know your dog. After all, Fred has never seen your dog or interacted with her in any way. You know your dog in a way that Fred does not. You have acquaintance knowledge of your dog; Fred doesnât.
Knowledge-how is different from acquaintance knowledge, and it at least seems to be different from knowledge of facts. Knowledge-how is the sort of knowledge common of abilities or skills. You know how to swim. You know how to throw a baseball. And so on. Knowing how to do something is different from having acquaintance knowledge, and it seems different from merely knowing facts. For instance, you might know all sorts of facts about how to swim and yet be in danger of drowning if youâre ever thrown into deep water! Conversely, you might be an excellent swimmer but completely incapable of expressing your ability to swim in terms of facts about swimming. (Relatively recently, a debate has emerged concerning whether knowledge-how reduces to knowledge of facts, but we can set that aside for nowâtraditionally the two have been taken to be different.)
Propositional knowledge (which we will simply refer to as âknowledgeâ in the entries that follow) is knowledge of facts. This knowledge is called âpropositionalâ because we mentally represent (think about) facts by way of thinking of propositions. In simplest terms propositions are what declarative sentences mean. Consider these three declarative sentences: âThe dog is brownâ, âEl perro es cafeâ, and âDer Hund ist braunâ. These three sentences are all declarative, but they are very different. They contain different words, and they are in different languages (English, Spanish, and German, respectively). However, they all mean the same thing. They all mean what we express with the English sentence âThe dog is brownâ. How can they mean the same thing though? After all, the sentences look completely different, and if they were spoken out loud, they would sound completely different. The answer to this question is that although these declarative sentences are different in important ways, they express the same proposition (which represents the same fact, namely that the dog is brown). It is the fact represented by the proposition that you know when you have propositional knowledge (for simplicity, we will later simply speak of knowing a true proposition). This is why an English speaker, a Spanish speaker, and a German speaker might know that the same dog is brown, even though they would express this knowledge differently by using different sentences.
Now, letâs take a closer look at the traditional account of propositional knowledge. This is sometimes referred to as the Justified True Belief (JTB) theory because it says that knowing that some proposition, p, just is having a justified true belief that p. Hence, in order for you to know that p, âthe dog is brownâ say, you must believe that p, p must be true, and your belief that p must be justified. It also says that any time you believe that p, p is true, and your belief that p is justified you know that p. Itâs worth briefly examining each of these three components of the traditional account of knowledge.
Belief. You might think that knowledge doesnât require belief because we sometimes say things that seem to suggest this. For example, if you were in an argument with someone who believes the Earth is flat, you might plausibly say: âI donât believe the Earth is spherical, I know it is!â It would be a mistake to take this as showing that you donât actually believe that the Earth spherical. Why? Because you behave the same way as someone who believes that the Earth is spherical does. You answer affirmatively if asked whether the shape of the Earth is a sphere. You are willing to use the proposition that the Earth is spherical in your reasoning, e.g. you reason that since the Earth is spherical, if someone were able to start walking in a straight line and do so long enough, she would end up where she started. So, the best explanation for why you might assert something like âI donât believe the Earth is spherical, I know it is!â is that you want to emphasize that this is not something that you merely believe. You are making it clear that this is something that you believe for good reasons, i.e. you have strong justification for accepting that the Earth is spherical. To make the general point clearer, think about your acquaintance Fred again, who not only doesnât believe the Earth is spherical, he actually believes that it is flat. Would we say that Fred knows that the Earth isnât flat? It seems not. Rather, it seems that we might say that he should know that the Earth isnât flat. Even if Fred is aware of all sorts of evidence for thinking that the Earth is spherical, it doesnât seem that he knows it isnât flat since he doesnât believe this. Hence, the traditional account of knowledge holds that belief is necessary for knowledge.
Truth. As with belief, there may be a temptation to think that knowledge doesnât really require truth. For example, when your team loses a big game that you thought you were going to win, you might say something like: âI just knew we were going to win.â Superficially, it seems that you are saying that you have knowledge of something falseâyou had knowledge that the team would win, but itâs false that the team would win. Is this the best way to understand what you are saying here though? It doesnât seem so. A much better explanation is that what you are really expressing is the fact that you were confident that the team would win or that you thought you knew that the team would win. In order to see this even more clearly, imagine that you and Fred, the flat earther, place a bet, the loser has to walk the otherâs dog. Fred bets that the Chicago Bears will win a particular football game, and you bet that they wonât. Assume (unfortunately, for many years this has been a safe assumption!) that the Chicago Bears in fact lose the game. You come to collect on your bet, but Fred responds, âI know that they won, so you have to walk my dog.â Would you think that Fred knows that the Chicago Bears won even though they didnât? Or would you think that Fred doesnât know what heâs talking about and needs to get to walking your dog? Presumably, youâd conclude that Fred doesnât actually know that the Chicago Bears won regardless of how convinced he is that they did. Why not? Because itâs not true. They didnât win, so Fred canât know that they did.
Justification. Weâve seen that knowledge requires true belief. Is that enough though? It seems not. Consider the following sort of situation: you and your new friend (talking about the JTB theory has led you to move from acquaintances to friends) Fred, the flat earther, are discussing another football game that neither of you watched. Neither of you has heard the gameâs final score, and you both know that the odds going into the game were even, i.e. it was predicted that the teams were equally likely to win. However, Fred decides to believe that the Detroit Lions won. You ask Fred why he thinks they won, and he responds: âNo reason, I just really want them to win, so I believe that they did.â Letâs assume that in fact Fred, by pure luck, is correct because the Detroit Lions really did win the game. Does Fred know that the Detroit Lions won before you and he look up the score? Surely not. Fred has no reason to think that the Detroit Lions rather than their opponents wonâhe is simply believing because of wishful thinking. Not only does Fred fail to know that the Detroit Lions won, but itâs also unreasonable for him to believe that they did. The rational thing for Fred to do is to suspend judgment about who won the gameâhe shouldnât believe the Detroit Lions won or believe that they lost. The rational thing is for Fred to not believe one way or other about the outcome of the game until he has some evidence about the score. Although Fred has a true belief about how the game went, he clearly doesnât know that the Detroit Lions won. Something more is needed for knowledge. This something more is justification. Roughly, justification amounts to having good reasons/evidence to believe something. Fred clearly lacks good reasons/evidence, so he fails to know. (For more discussion of justification, see General Background: The Nature of Justification pp. 113â119.)
We can put these insights together to get a precise formulation of the traditional account of knowledge:
Someone, S, knows that p if and only if: (1) S believes that p, (2) p is true, and (3) Sâs belief that p is justified.