René Descartes (1596-1650) argued that we cannot be certain of the truth of any of our beliefs about the external world. Our only reason for believing in the existence of the physical world, after all, consists in our experiences. All our beliefs about the physical world are based on our experiences of the physical world.
But an evil demon could give us these very experiences without there being a physical world to make the beliefs we base on these experiences true.
George Berkeley (1685-1753) accepted Descartes’ argument, to the extent that he believed we could be certain only of the existence of our experiences. But Berkeley rejected Descartes’ claim that this entails we know nothing about the physical world.
All we have to do, claimed Berkeley, to justify our claim to have knowledge of the physical world, is to recognise that physical objects are constituted of experiences.
To be, said Berkeley, is to be perceived (“esse est percipi”). We will never have any reason for thinking that a physical object exists that doesn’t consist in a set of actual and counterfactual experiences (counterfactual: if I had been there I would have seen it).
Can we undermine Descartes’ claim that we cannot be certain of the truth of any of our beliefs about the external world?
If not must we accept either Berkeley’s claim that physical objects are constituted of experiences, or the position of the sceptic (i.e. we cannot know about anything other than our own experiences?)
Descartes, R: The Meditations on First Philosophy, Meditation 1
A ‘Modern’ version: http://www.earlymoderntexts.com/pdfs/descartes1641_1.pdf
Berkeley, G: A Treatise Concerning The Principles of Human Knowledge 1-33
A ‘modern’ version:
An audio version:
Williams, B: Descartes: The Project of Pure Enquiry, chapters 1&2
Foster, J: ‘Berkeley on the Physical World’ in Foster and Robinson’s Essays on Berkeley