Hume: Skepticism about Justified Belief (handout)

1. Skepticism about knowledge does not entail skepticism about justified belief. So we can abandon the claim that we have (any) knowledge without giving up the idea that (some of) our beliefs are rational.

• Skepticism about knowledge: "Knowledge is unobtainable; we can never be certain about anything we believe."
  
  
• Skepticism about justified belief: "We are not rationally justified in believing what we do."

2. David Hume argues that beliefs we have about the future (predictions) and even general beliefs we form about our observations cannot be trusted. So Hume is a skeptic about justified belief. He thinks there is absolutely no rational justification for beliefs that are generalizations or predictions!

It isn't merely that we can't be certain that the sun will rise tomorrow. And it is not just that we don't know that the sun will rise tomorrow. According to Hume, we have no rational justification at all for this belief or any other expectation about the future. Why not? It seems reasonable to believe this, sure, but it is not unreasonable to disbelieve it too.

3. Ask yourself this: Might an expected event NOT happen as we believe? If so, then why do we believe otherwise?

Common sense suggests that it is rational to believe the generalizations and predictions that we do IF those beliefs are based on lots of empirical evidence. But Hume thinks our inductive inferences are never justified, either a priori or a posteriori, since in either case we presume too much. Merely by habit or custom do we regard such premises as providing good reason to believe such conclusions.

Consider the following allegedly strong inductive arguments: Can you state the missing premise in each?

- Why do we think these conclusions are justified? State missing principles explicitly...

4. Why induction cannot be justified (Hume):

1. Every inductive argument (IA) assumes that the future will resemble the past (PUN).
   
2. If the conclusion of an IA is rationally justified by the premises, then those premises themselves must be rationally justifiable.
   
3. If the conclusion of an IA is justified, then there must be either a good IA or a good deductive argument (DA) for PUN.
   
4. But, there is no good IA for PUN since any such argument will be circular (presuming in advance what it is intended to prove).
   
5. There also cannot be a good DA for PUN, since PUN is not a priori true (i.e., known by reason alone), and PUN does not deductively follow from observations we have made thus far.
   
6. PUN is not rationally justifiable.
   
7. There is no rational justification for those beliefs we express in predictions or generalizations (i.e. IA conclusions).
   
   

5. How then can such beliefs be justified? Answer: they cannot, at least not philosophically, however we are psychologically impelled to accept PUN.

6. Thus, inductive arguments, which produce conclusions that are either generalizations or predictions, must assume that the future will resemble the past [PUN].

But, given Hume's argument (is it deductive or inductive?) it looks as if the inductive beliefs we have about emerald color, tomorrow's sunrise, falling stones, and billiard ball interactions are not rationally justifiable, because they rely upon an assumption that can't be rationally justified.

Other versions of PUN: "The future resembles the past." "Similar effects have similar causes..." "The way things are is the way they are always going to be." "Past performance is an indicator of future performance..."

• Hume shows that empirical evidence never adequately justifies believing inductive conclusions, because the premises of any inductive argument do not logically imply its conclusion unless we assume what we cannot prove.

7. What justifying principle do YOU rely upon for accepting/justifying such claims?

• "If an authority said it, then one should believe it."
• "I should accept as true whatever I cannot reasonably doubt."
• "If I cannot doubt P, then I must believe P."
• "If it is reasonable to doubt G, then I do not accept G."
• "Whatever one cannot justify believing, one ought to reject."
• "If I believe it then it is true."
• "If we believe it then it is true."
• "If we want to believe it then it is true."
  
  

8. Source: Hume's Enquiry Concerning Human Understanding (1748), Section IV: Sceptical Doubts Concerning the Operation of the Understanding

• nice intro to Hume's position here: en.wikipedia.org/wiki/Problem_of_induction