Rationalism

1 Possible responses to the regress

One possible response to the regress is to accept that it is sound and become a sceptic. But that is itself problematic, since one would be adopting a position (scepticism) on the basis of a rational argument. One would be effectively saying "On the basis of this clever argument I now have a very good reason to believe that I know nothing at all." That's queer, because the thoroughgoing sceptic presumably thinks we have NO good reason to believe anything that is in fact true. If he did think we had one good reason for thinking that some particular proposition is true, then he would have to accept that there are some justified true beliefs, and that goes a long way to conceding the possibility of genuine knowledge.

The sceptical regress involves three crucial assumptions:

(1)    the principle of begging the question;
(2)    the principle of the accessibility of good reasons;
(3)    the JTB theory of knowledge;

Different epistemologies are generated by rejection one or other of these three assumptions.

2 Rejecting the regress

In order to defeat the sceptical argument it seems that the regress must come to halt. One of the three key assumptions is the first principle of not begging the question:

P is never a good reason for P itself.

The sceptic argues that to offer P as a good reason for believing P itself is to beg the question. But perhaps that sceptical claim is a bit swift. It may be that some truths simply do not need any justification other than the justification they themselves wear on their sleeves. In other words, some truths may be simply self-evident. Self-evident truths would not require any justification. If there were such truths then they could constitute a foundation for all other knowledge.

Those who think that the principle is false, and that knowledge does possess a foundation of self-evident truths which halt the sceptical regress, can be called foundationalists. Foundationalists fall into two main categories. Some think that the self-evident truths which form the foundation of all knowledge are revealed to us by reason alone. These are called the rationalists. Others think that the self-evident foundations are to be found in sense experience. These are the empiricists.

One could also reject the principle of the accessibility of good reasons. One example of such a theory is realisabilism: the idea that a true belief is knowledge if the belief is generated by a reliable mechanism. That it is generated by a reliable mechanism seems to be a good reason for believing it, but one might not have independent access to that good reason. For example, sense perception may be a reliable generator of true beliefs, but one does not have to know that it is in order to have knowledge on the basis of sense experience.

Finally one could reject the JTB analysis of knowledge. For example, one might claim that knoweldge does not require justification of good reasons. One might claim that what is important to knowledge is simply getting it right (true belief). So knowledge might be quite conjectural, and even fallible, without ceasing to be knowledge. Sometimes this position is calle fallisbilism.

Obviously, I am oversimplifying here. For example, it is usual to classify the philosophers Plato, Descartes, Leibniz, and Spinoza as rationalists, and to classify the philosophers Locke, Berkeley and Hume as empiricists. But there will be philosophers who are difficult to categorize, and many features of the philosophy of those mentioned do not fit so easily into the above map. There are philosophers who entertain both reason and the senses as sources of knowledge: for example, Kant. There are philosophers (perhaps Plato) who recognize other sources of, and foundations for, knowledge.

3 Descartes's rationalism

The seventeenth century French rationalist Descartes wanted to push doubt to the extreme to see what, if anything, would survive. He discovered that there was one proposition which he could not possibly doubt: he could not doubt that he himself doubts. Putting all this in the first person, I cannot doubt that I doubt. For if I doubt anything then I thereby demonstrate that I doubt. So the proposition I doubt or I think is one the mere contemplation of which is sufficient to guarantee its own truth. This is Descartes' famous cogito: that is just Latin for 'I think'. Now since it is impossible for me to doubt or think without also existing, it is also indubitable (for me) that I exist. As Descartes put it: cogito ergo sum: (Latin for 'I think, therefore I am'). This seemed, to Descartes, to provide a foundation for knowledge. And note that it is a foundation which does not rely in any way on the information we get about the world through the senses. Even if my sense experiences are wholly deceptive I can still be sure that I think and that I exist.

We could argue about Descartes' foundation, but we won't. I want to press on here. It is all very well having a foundation stone, but for it to be worthwhile you have to build something on it. Descartes, thought, of course, that that could be done. In particular he thought we could have knowledge not only about ourselves but also knowledge of God, and knowledge of the external world. Moreover, he thought we could gain that knowledge of the world through sense experience, although to know that the senses yield knowledge we have to trace our justifications back to the foundation.

How does Descartes know that the senses are a reliable guide to the truth about the world? In order to guarantee the reliability of the senses Descartes appealed to the goodness of God. Surely a perfectly good and all-powerful God would not systematically deceive us about the nature of the world by endowing us with faulty senses? But here is a problem (the problem of justification again): how does Descartes know that God exists? At this point Descartes uses his famous ontological argument. And so you can now see why Descartes thought it important to have an a priori proof of God's existence: one which does not rely on the details of sense experience. He wanted to give a foundation for knowledge in reason alone. The senses do provide us with information, but we can be confident that it is accurate information only because we can be confident that God exists and would not deceive us: and we know that God exists by reason, not through sense experience.

Descartes has a problem with error and ignorance. If the reliability of the senses and of reason can be inferred from the goodness of the creator, whence ignorance and error? These become part of the more general problem of evil. And Descartes' solution is an instance of the free-will defense. He argues that the senses and reason do not themselves lead us into error. Rather , it is our own freely-chosen judgement on what the senses and reason present to us which gets us into trouble. Ignorance and error are thus species of sin for Descartes.

The trouble with Descartes's theory of knowledge is that his little island of certainty, the cogito, is just too small. We cannot get from it to some large continent of certainty. The leap to God from the cogito is a huge one, not a small one. And from there to the reliability of the senses seems even bigger.