enter image description here

This is from Philosophy & Ethics For Dummies 2 eBook Bundle. I cannot actually understand this text fully. It seems that there's some illogical part. (Sorry if there's no such thing)

Especially 'But how ~ reliable? part is puzzling.

  • can you make your question clearer? Also can you indicate the source of the page image?
    – virmaior
    Aug 17, 2017 at 2:32
  • books.google.co.kr/…
    – siho lee
    Aug 17, 2017 at 2:47
  • On 7th line from the bottom says 'But how could any ~ them are sometimes reliable?' As you can see by original text, it says that 'by an Independent rational principle, certain basic beleifs can be accepted rationally without evidence or proof.(in original text, 3 line below from the last sentece of captured image) At first it says that 'rational' belief must entail reliable sources or mechanism But at last it says that in some case evidence is needless. For me, it doesn't make sense.
    – siho lee
    Aug 17, 2017 at 3:03
  • Also, In the same sentence I mentioned above, it says '~through which we received them are sometimes reliable'
    – siho lee
    Aug 17, 2017 at 3:05
  • 1
    Why 'sometimes'? Why word 'sometimes' must have been put on that sentence?
    – siho lee
    Aug 17, 2017 at 3:06

1 Answer 1


Roughly, the text means we have to put some faith into our sense-data. I'll translate what I take to be the best reading into plainer terms.

As we seek to understand more deeply our common conception of rationality, we can make some interesting observations.


First, our beliefs can't be irrational, or nonrational, or else the concept of rationality has no application at all.

We shouldn't hold irrational or nonrational beliefs. This is a requirement of rationality. If rationality did not forbid irrationality, it wouldn't do anything at all.

The concept of rationality derives its usefulness from its ability to demarcate some beliefs off from others, separating the sheep from the goats, or the wheat from the chaff.

This is evidence for the previous sentence; rationality needs to be able to discriminate between good and bad beliefs.

But how could any of our beliefs be rational unless it's rational for us to assume that the sources or mechanisms through which we received them are sometimes reliable?

Let's go out on a limb and say, hypothetically, that we have some rational beliefs. A rational belief is a belief held for rational reasons, that is, a well-justified belief. A belief couldn't be justified if there were no way to even occasionally acquire justified beliefs.

It must then be rational to hold that our basic belief-forming mechanisms---sense experience, memory, and the testimony of others, for example---are sometimes reliable.

Of course we do have some rational beliefs, so we have to put some trust in the mechanisms by which we acquire beliefs. But of course we also have some irrational beliefs, so we shouldn't just trust in our ability to form beliefs blindly. In fact, we can be certain that our belief-forming mechanisms are sometimes unreliable, or else we would never have wrong beliefs.

And if this rationality does not consist in our having a proof, or even any good evidence, for the truth of the proposition believed... then there must be some other road to rationality, other than proof and evidence.

This sentence is unclear and iffy. I'm not sure why the beliefs formed by the already-mentioned mechanisms wouldn't be supported by evidence. The testimony of others, our senses, and our memories all seem to me to be evidence that a belief is accurate. But I suppose we'll have to wait for Chapter 5 to really understand what the author is talking about.

  • i'm glad that your answer was well received, but was a little unsure (only) on "we can be certain that our belief-forming mechanisms are sometimes unreliable, or else we would never have wrong beliefs". can't a mechanism be 100% reliable, yet output some trash? perhaps it is reliable because it achieves its aim, or perhaps the source of our beliefs work but we deceive ourselves
    – user28117
    Aug 17, 2017 at 3:58
  • The aim of belief formation is the formation of true beliefs.
    – Canyon
    Aug 20, 2017 at 0:37

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.