PHL A10 - Exercise VIII
1. What does Sober mean by the "internal certifiability" of knowledge?
Internal certifiability means that if S knows some proposition P, then there exists an argument that shows that P
must be true, whose premises are either a priori true or knowable by introspection. Introspection is gained by
going within one’s mind and examining its contents. The subjective premise describes what is going on in the
subject’s mind. The objective conclusion makes a claim about the world outside the subject’s mind. The linking
premise shows how the subjective premise necessitates the objective conclusion. If the subject knows that the
objective conclusion is true, then the subject must know that the linking premise is true and must know this
independently of sense experience.
2. Why is reliability an objective feature of some information carriers and the environment?
Reliability is an objective feature of some information carriers and the environment because reliability has
nothing to do with what one imagines. If the situations imagined were actually obtained, then it would be
unreliable under those circumstances. This is best explained with the analogy of the thermometer. I f the
thermometer says that the temperature is n degrees, then the temperature must be n degrees. It is an entirely
separate question whether anybody realizes that this thermometer/environment relationship obt ains. Whether we
notice this fact is a subject question, but whether the relationship obtains is an objective matter.
3. What's the key difference between the reliability theory of knowledge and the traditional justified true
belief theory of knowledge?
The difference between RTK and JTB is that RTK makes use of the concepts of necessity and impossibility. In
RTK, the third premise states that in the circumstances that S occupies, if S believes that P, then P must be true. In
JTB, the third premise states that S is justified in believing P. A statement is nomologically necessary when i t is
not a priori and it is necessary because of a law of nature. Circumstantial necessity is a statement that is
necessarily true only because of facts about the circumstances described.
4. What is the "KK principle"? (Think about whether you think it is true.)
The KK principle states that knowing a proposition implies that you know that you know it. I f S knows that P,
then S knows that she knows that P. Therefore, it is also true that if S knows that P, but S doesn’t believe that she
knows that P, meaning S might know that P even though she doesn’t know that she knows P. Thus, making the
KK principle false. If the KK principle were true, S could prove that she lacked knowledge just by becoming a
philosophical skeptic. Therefore, believing that skepticism is true would be enough to ensure that skepticism is
true. The reliability theory of knowledge rejects the KK principle.
5. How would the reliability theory of knowledge reply to a skeptic who claims that one might just be
The reliability theory of knowledge explains what is wrong with a standard skeptical argument. The skeptic
claims that S doesn’t know that P on the groups that it is possible to imagine that S is deluded in some way. It is
possible for a situation to exist in which S believes what she does, but is mistaken. The reliability the ory shows
why this act of imagination is irrelevant to the question of whether S has knowledge in the real world situation she