Christopher asked:

We say that faith is unjustified, but don’t we have faith in reason and logic? We always base our beliefs, which we consider to be true, on our past experiences and we assume (i.e. have faith) that our future/ present experiences will be similar. We believe that if we drop a pencil it will fall because that is what has always happened, and it still takes faith to believe it will happen again. If this is true then what can we base our knowledge on?

I’m aware of Descartes proof of the existence of the self, but even this can only be true if reason itself is infallible, which I seriously doubt. A philosopher once showed that motion is an illusion using reason and logic. Paradoxes exist. We have numbers that are non-repeating and nonterminating, yet correspond to something finite and material. I’m using reason to show that reason is infallible and if the rules of reason imply that reason is unreasonable (untrue) then something seems to be wrong. Am I right?

Answer by Craig Skinner

Your question bears on the ‘epistemological turn’ in philosophy which began with Descartes, continued through Locke, Berkeley, Hume, Reid and Kant, and was reinvigorated by Gettier and Quine fifty years ago.

You are right about one thing. We can have no absolutely certain knowledge. Ultimately we base our beliefs on reason or perception. Both can be faulty, and we can’t prove that either produces true beliefs. Reason can only be justified by reason, a circular argument which Descartes is guilty of using, as you say

But this doesn’t mean it is unreasonable to rely on our considered beliefs, or that they are wrong. Most of them may well be right. It’s just that we can’t prove them, so that, as you say, we are fallible, we must live by faith (understood as reasonable assumption not as blind faith going against all evidence)

Let’s briefly consider induction, reason and perception.

First, induction. Yes, it takes faith to believe the pencil will fall next time I drop it. So what. The whole of nature relies on induction in the sense that past regularities are hardwired into genes and brains. Right now the tree in my garden is shedding its leaves, in anticipation of winter, and in a few months, will sprout new ones, in anticipation of summer. My dog is looking at me expectantly as the time for her walk draws near. And I don’t think the tree or the dog will be disappointed. Of course, As Hume says, we can’t justify the necessity postulated by causation or laws of nature, and so can’t be sure the future will be like the past. Moreover, even if we do accept a necessary connexion between constantly conjoined events, this has only been up to now, and we can’t be sure it will hold in the future. But it is still reasonable to rely on it, we all do, we can’t do otherwise, as Hume himself says.

As for reason, there has been a traditional presumption in philosophy that truths of reason (analytic, necessary, apriori), although not telling us anything about the world, are especially reliable. Whereas, truths arrived at by observation (contingent, a posteriori), although telling us about the world, are less reliable. I suggest that because neither reason nor perception can ultimately be justified, all truths are on a par. On this I side with Thomas Reid and Quine. As Reid says:

‘Why, sir, should I believe the faculty of reason more than that of perception? – they came both out of the same shop, and were made by the same artist: if he puts one piece of false ware into my hands, what should hinder him from putting another?’ (Reid T [1764]: An Enquiry into the Human Mind on the Principles of Common Sense).

Reid’s point holds whether we regard (with Descartes) the ‘artist’ as God, or (with Hume and Darwin) as nature

As for perception, as I say (with Reid, Moore and Quine), it is on a par with reason. To be sure, we can’t PROVE the external world exists. But (as GE Moore said, and illustrated by his notorious ‘hands’ argument), we don’t know about things in the external world by proof, we know about them by perception.

So, I go for a moderate, wide, foundational, naturalistic epistemology: moderate, in that I am content with fallible knowledge; wide in that I know of an external world, other minds and moral truths; foundational in that my belief system is supported by basic beliefs founded on reason and perception; naturalistic in that I think evolution has seen to it that my perception and reason are generally reliable.

Finally, I wont deal here with paradoxes of motion or issues to do with irrational numbers, except to say that I think any paradoxes arising are only apparent logic inconsistencies, not real ones when considered in depth (Achilles is not really still chasing that tortoise!). So, I don’t think ‘the rules of reason imply that reason is unreasonable (untrue)’ as you put it.