I begin as Descartes did, with the knowledge that I exist: ‘I think therefore I am’. What else exists? Everything I experience must exist in some way, even if it’s simply as my experiences. So I divide my experiences into the sorts of things that depend on me for their existence, and those that do not. The former are my sensations, feelings, and thoughts. The latter constitute what I call ‘the world’. I experience the world as other than myself and independent of me, and conclude that most external things that I believe exist do exist. How do they exist? That is, in what way? They exist much as I believe they do (with some help from science). That things exist much as I believe they do is the simplest…
