1 Knowledge
First, let’s ask what sorts of things are “known” in the sense we are interested in. In a claim of the form “Sluggo knows X,” what sort of entity goes into the “X” spot? We could fill in the blank with phrases like “how to ride a bike,” “how to speak Esperanto,” or “how to dance like a maniac.” These are abilities Sluggo may or may not have, and we might call this sort of knowledge know-how. Philosophers typically are not very interested in know-how since we have not yet come across many interesting questions or problems to raise about it. Instead, we could put into the “X” spot phrases like “that Bangladesh and India share a border,” or “that Jupiter is larger than Mars,” or “that Francis Bacon is credited with having said that knowledge is power.” For obvious reasons, this is called knowledge-that, and what is known, or what goes in the “X” spot, are claims that may be true or false which philosophers call “propositions.” Philosophers are very interested in propositional knowledge.
So, let’s continue to focus on propositional knowledge. We will want to know what features a proposition has to have in order for us to rightly say that someone knows it. We have already seen one back when we were observing that people sometimes fight over knowledge or truth. A claim to know X is, among other things, a claim that X is true. No one would ever claim to know something they believe is false. (Well, they might if they were lying. But if they were not trying to lie, and they were well aware of what they are saying, and they were not under the influence of some strange drug or head injury, they would never say, “I know X and I think X is false.”) Furthermore, we would not claim that someone else knew something if we thought that that something were false. I would not say that Sluggo knows the world is flat since the world isn’t flat. Sluggo might believe it is, but he does not know it, because it isn’t.
This is a tricky point, so we should spend a little more time on it. Some time ago, people thought the sun revolved around the earth. They had good reason for believing this since it certainly looks like the sun revolves around the earth at the rate of once per day, and we do not feel the earth to be in motion. But would we say these people knew it? They believed it, yes, and they had their reasons, yes, and they thought they knew it, yes. But did they know it? We might say they “knew” it, but it would be important to keep those scare-quotes attached because they did not really know it. They did not know it because the claim is false, and they were wrong.
(Or so it seems to me. But at the very least there is one widespread meaning of the word “know” which implies that what is known is in fact true, and in what follows, that is the sense of “know” we will be using.)
This discussion also suggests a further feature of propositions we claim to know: we must also believe them, or in other words, believe they are true. There may be some cases of peopl