Reason and Experience: Introduction

Where does our knowledge come from? How do we acquire it? Epistemologists argue about what knowledge is – ie what its necessary conditions are. Is it, for example justified true belief? What properties must a mere belief have before we can count it as knowledge?

Epistemologists also argue about whether knowledge is a unitary concept: is knowing that Obama is the US president the same kind of thing as knowing how to swim or knowing your neighbour (knowledge by acquaintance)? But the arguments we are concerned with are about the sources of knowledge.

No doubt a great deal of what you know has come from other people (friends, parents, teachers) telling you things – ie testimony. Some people think they know things as a result of revelation – it has been revealed to them by a vision, or voices or a miracle. We might argue that our own memories can be a source of knowledge for us. But the main arguments traditionally have revolved around the claims that rationalists have made for reason as the primary source of knowledge, and the claims made by empiricists for experience as the only true source of knowledge.

On the whole, empiricists argue that none of our ideas come from reason alone, whereas rationalists argue that some do. Rationalists concede that much of our knowledge depends on sensory experience, but insist that the true foundations rest on what we know by reason alone.

Rationalism argues that we can know things by reason alone: thinking can give us truths without help from our senses. The truths of maths and logic are often used as examples. A solitary thinker sitting in front of his fire, with a candle burning by his side – Descartes’ meditator – can discover certain truths in his own mind. His senses may deceive him, he may be the victim of the tricks of an evil spirit, but certain clear and distinct ideas or intuitions can give him certain knowledge. In this way Descartes’ meditator achieved certain knowledge of his own existence and of the existence of God (the cogito argument and the ontological argument). He also discovered in himself innate knowledge of God(the trademark argument). He was then able to use such certainties as foundations on which to build a secure body of knowledge – the existence of the external world, science, etc.

So the twin claims of rationalism are that we can have knowledge without help from the senses (a priori knowledge) and we have a certain stock of innate knowledge or innate ideas (eg God, morality, rules of reasoning). These are separate claims and it is important not to confuse them. We could reject one without necessarily having to reject the other.

Two separate claims can be differentiated in the a priori claim: firstly, that substantive knowledge (facts) can be achieved by pure thought or intuition, and, secondly, that analytic truths can be known without sensory input – they are true by definition. Again, we could reject one without having to reject the other.

Both traditions, rationalism and empiricism, have generally (until the twentieth century) been forms of foundationalism. This is the idea that we justify our beliefs or claims to knowledge by connecting them to chains of reasoning going all the way back to basic foundational beliefs, the ones you can’t go beyond. For empiricists the basic foundation of all knowledge is sense experience – the raw sense data that comes into our mind from the outside world via our five senses. This is the Given; it is immediate, incorrigible, present. Rationalists argue that we can’t trust our senses: they can deceive us, so they cannot provide secure foundations for our judgements; absolutely certain knowledge can rest only on what we discover in our minds by pure thought.

One of the problems for empiricists is to explain how propositional knowledge (knowledge that p) can be built on perceptual experience, which is knowledge by acquaintance. But then rationalists have to explain how it is that we can discover propositional knowledge already in our minds. How did it get there? The problem for both traditions is to explain how something that is subjective and private (sense experience or thoughts) can be the foundation of something that is essentially public and shareable – knowledge.

At the end of the eighteenth century Immanuel Kant tried to reconcile rationalism and empiricism through his idea of an innate conceptual scheme, and in the twentieth century philosophers have questioned foundationalism and the possibility of founding knowledge on private experiences. Various versions of coherentism argue that beliefs are only ever justified by other beliefs: what you belief is justified and rational when it fits into your existing web of beliefs. There are no foundations. This opens the way to relativism about truth and knowledge.

The starting point for all modern philosophy is Descartes’ cogito ergo sum argument in Meditations. It was published in the 1640s at the dawn of the new age of experimental science, which combined observation and experiment with mathematical reasoning – in other words, it combined the empirical with the rational. Particular empirical observations needed to be generalised into theorems, principles and laws of nature. Descartes and others considered that you need the empirical data but you also need to interpret the data in the light of the general, universalisable truths that rational methodologies have discovered. Observation gives us data but reason gives us understanding. So the philosophical debates about reason and experience have real significance for science, for how we interpret the world to ourselves. Empiricists and rationalists have to achieve generalised truths or laws of nature in different ways.

Another key moment was when John Locke, towards the end of the senventeenth century, rejected innate ideas and argued that we are born without any ideas or knowledge- the tabula rasa argument. So, what are the key arguments for and against innate ideas?