Descartes

Descartes took the idea that we are very limited in what we can know about reality to an extreme and came up with the idea that the only thing we can know for certain is that we exist, simply from the fact that there is someone having the thoughts and experiences. This can be taken a step further by recognising that the thinking someone has experiences of various kinds.

We know from first hand experience that we are conscious entities who have experiences such as pain and pleasure, perceptions of red and blue, high and low pitches of sound etc. These phenomenal experiences are either self-generated, which implies at the very least that we are complex beings, or that there is a universe, whether actual or virtual, which is external to us and separate from us which is causing, or at least influencing, the experiences.

The first option leads to solipsism, the view that we are alone in our universe. This is logically possible but leads to a dead end so will not be pursued here.

That the experiences are caused by an external world is supported by the fact that they have structure. Pain is almost always centred on a particular part of our perceived body. Rather than simply seeing colours, we see images which we identify with objects in the external world.

We are know from first hand experience that, by thinking in particular ways, we can influence our experiences. For instance, by thought, we can raise our hand. We then experience the image of our raised hand and, if that causes our hand to touch something, we experience the sense of touch.

Although it can be inferred that there is a world external to us which is causing our experiences and which we can influence by our thoughts, the nature of this world is unknown. How our thoughts and experiences map onto that external world cannot be known. What we are able to do is investigate the experiences, how they relate to each other, how they are affected by our thoughts, and come to conclusions about them. We can then learn how to use our thoughts to influence our experiences in a way which makes them more as we would like them to be. For this purpose, the nature of the external world does not matter.

Approximate models of the perceived world

It is to this data set that we apply our knowledge collecting abilities and methods to construct models of. By making more and more experiments, we can get better and more accurate models with greater predictive and explanatory power, but they remain models and are not complete or infallible.

Knowledge has been defined as “justified true belief” derived from Plato’s Theaetetus. However “justification” is not a binary thing. Evidence can be produced to support a hypothesis which will itself be subject to uncertainty, some more than others. Therefore it can give a greater confidence to the hypothesis but never certainty. Knowledge is always partial. Even if the evidence is overwhelmingly likely to indicate that what is believed is true, there is always some doubt, even if vanishingly small.

This is expressed by Feigl [1 page 38] who says there can be no certainty. Ziman [2,page 10] describes the scientific investigation as of successive approximation.

Simpson [3]- scientific explanation.

In order to make concrete progress, some assumptions have to be made.

A list is suggested by Searle which he calls “the background” and are the following [4,page10].

• There is a real world that exists independently of us, independently of our thoughts, experiences and languages.
• We have direct perceptual access to that world through our senses especially touch and vision.
• Words in our language typically have reasonably clear meanings. Because of their meanings they can be used to refer and to talk about real objects in the world.
• Our statements are typically true or false depending on whether they correspond to how things are, that is, to the facts in the world.
• Causation is a real relation among objects and events in the world, a relation whereby one phenomenon, the cause, causes another, the effect.

Although these may appear self-evident, they have all been challenged at one time or another and not all of them are believed by everyone. They are reasonable and consistent with observation but none of them can be proved.

In addition to the above, we can add this:

• The external world behaves consistently according to laws at least over a time period much greater than the observation time of any individual. Moreover, it is possible to deduce these laws using scientific investigation.

In the above, the “external world” would exclude any entities which have agency or free-will, such as other people. They, by definition, would not follow fixed rules.

1. Feigl 1953: Herbert Feigl, The Scientific Outlook: Naturalism and Humanism, 1953
2. Ziman 1980: John Ziman, What is Science?, 1980
3. Simpson 1963: George Gaylord Simpson, Historical Science, 1963
4. Searle 1999: John R. Searle, Mind, Language and Society, 1999