XIII: Knowledge, Error, and Probable Opinion explained

What happens

Themes in this chapter

• Truth and Falsehood

  The chapter builds on the previous chapter's definition of truth, applying it to the problem of distinguishing knowledge from error.

• Knowledge and Certainty

  Central theme: the chapter investigates what it means to 'know' something, the degrees of certainty, and the role of self-evidence.

• The Value of Philosophy

  Implicitly addressed through the recognition that all knowledge is infected with doubt, highlighting the philosophical quest for understanding rather than absolute certainty.

Characters to notice

• Socrates

  Used as an example in a syllogism about valid deduction: 'If I know that all Greeks are men and that Socrates was a man, and I infer that Socrates was a Greek, I cannot be said to know that Socrates was a Greek.'

• Othello

  Referenced in the discussion of self-evidence and acquaintance: 'When Othello believes that Desdemona loves Cassio, the corresponding fact... would be Desdemona's love for Cassio.'

• Desdemona

  Mentioned as the only person who could have acquaintance with the fact of her love for Cassio, illustrating the privacy of mental facts.

• Cassio

  Referenced as the object of Desdemona's love in the example about belief and self-evidence.

Key passages

• “There can be no doubt that some of our beliefs are erroneous; thus we are led to inquire what certainty we can ever have that such and such a belief is not erroneous.”

  Because we know some beliefs are wrong, we must ask how we can be sure any belief is correct.

  Opening motivation for the chapter's inquiry into knowledge and error.

• “If a man believes that the late Prime Minister's last name began with a B, he believes what is true, since the late Prime Minister was Sir Henry Campbell Bannerman. But if he believes that Mr. Balfour was the late Prime Minister, he will still believe that the late Prime Minister's last name began with a B, yet this belief, though true, would not be thought to constitute knowledge.”

  A true belief based on a false premise, like thinking Balfour was Prime Minister and thus that the PM's name started with B, is not considered knowledge.

  Illustrates that true belief is insufficient for knowledge if derived from error.

• “We may say: 'Derivative knowledge is what is validly deduced from premises known intuitively.'”

  Derivative knowledge is defined as conclusions correctly drawn from premises that are intuitively known.

  Provisional definition of derivative knowledge, leaving intuitive knowledge to be defined.

• “Thus although a valid inference from the letters to their meaning is possible, and could be performed by the reader, it is not in fact performed, since he does not in fact perform any operation which can be called logical inference. Yet it would be absurd to say that the reader does not 'know' that the newspaper announces the King's death.”

  Even if a reader doesn't consciously reason from the print to its meaning, we still say they know the news, so knowledge can arise from psychological inference alongside logical inference.

  Expands the definition of derivative knowledge to include psychological inference.

• “When a belief is true, we said, there is a corresponding fact, in which the several objects of the belief form a single complex. The belief is said to constitute 'knowledge' of this fact, provided it fulfils those further somewhat vague conditions which we have been considering in the present chapter.”

  A true belief counts as knowledge only if it also meets additional, somewhat imprecise conditions discussed in this chapter.

  Summarizes the relationship between truth, belief, and knowledge.