Student Material

Chapter 8: Truth, knowledge and belief

Students’ material


Indicate whether the following claims are true or false.

  1. We can only know a proposition if it is true.
  2. We cannot believe a proposition that is false.
  3. If someone does not believe some proposition, p, they must believe its negation, not p.
  4. A true belief that p is sufficient for knowledge that p.
  5. All truth is relative.
  6. Some truths are speaker relative.
  7. To count as knowing that p, I must be justified in believing that p.
  8. The sentence ‘It is raining here’ includes an indexical.
  9. It is possible to have a justified false belief.
  10. According to the tripartite account of knowledge, knowledge is justified true belief.


Indicate whether the following sentences are indexical, implicitly speaker-relative or neither.

  1. It’s very sunny here today.
  2. This exercise is too easy.
  3. Tony likes Brenda better than he likes Mavis.
  4. Brenda is more beautiful than Mavis.
  5. Jakarta is east of Cape Town.
  6. Don’t put it there!
  7. According to these test results, he’s smarter than you.
  8. It’s going to rain in Bristol on Tuesday.
  9. It’s raining there.
  10. That’s a great dress – where did you get it?


Consider the following scenarios and then answer the questions that follow.

  1. Heather experiences hallucinations. As a result of such, she forms the belief that her sister, Helen, has given birth to triplets. As a matter of fact, Helen has given birth to triplets, but no one has informed Heather.
    a) Is Heather’s belief that Helen has given birth to triplets justified?
    b) Does Heather know that Helen has given birth to triplets?
    c) If there were a valid or inductively forceful argument, one of the premises of which was the proposition that ‘My sister Helen has given birth to triplets’, would Heather have good reasons for accepting that premise?
  2. Jock is deeply interested in politics, particularly at election time. He tracks opinion poll data, goes to all the meet-the-candidates meetings, watches televised debates and attends rallies. Jock has found that all of this activity has made him proficient at predicting the winners of elections and he often places bets on the likely outcomes. Jock has been closely watching the contest for the Senate seat in the state of Boredom. He’s pretty confident that he’s picked the winner – the seat will go to Marjory Yapp; all the opinion poll data and anecdotal evidence that he’s picked up along the campaign trail points in that direction. Jock forms the belief that Marjory Yapp will win the seat and he places a $1,000 bet on that outcome. However, while Jock spends a lot of time and energy keeping himself up-to-date with media coverage of politics, he’s doesn’t tend to bother with gossip websites. One such, the Grudge Report,is reporting that Ms Yapp has pulled out of the race because her husband, president of an investment bank, is involved in a sub-prime lending scandal, but Jock doesn’t see this report and places his bet. The next day, the Grudge Report’s story is confirmed in the mainstream media and Jock is $1,000 down.
    a) Does Jock have a justified belief that Marjory Yapp would win the seat?
    b) Is that belief true?
    c)  If there were a valid or inductively forceful argument, one of the premises of which was the proposition that ‘Marjory Yapp will win the seat, would Jock have good reasons for accepting that premise?
    d) If that argument were inductively forceful and Jock had good reasons to believe its premises, would it have been defeated for Jock had he seen the Grudge Report article about Mr Yapp?
  3. Consider the same scenario, but this time imagine that Jock is following a Senate race in the state of Happiness and there are two female candidates, Marjory Yapp and Yvonne Mapp. On the basis of all the evidence he has studied, Jock thinks that Marjory will win and he forms the belief that a woman will win the seat. However, for the reasons outlined above, Ms Yapp pulls out of the race and Yvonne Mapp takes the seat.
    a) Is Jock justified in believing that a woman will win the seat?
    b) Is that belief true?
    c) Does Jock know that a woman will win the seat?
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