stephen radix is a user on mastodon.observer. You can follow them or interact with them if you have an account anywhere in the fediverse.
> There is some external physical world capable of exciting the mind, but the contents of the mind are just copies, or simulacra, of what is occuring at the level of sensation. We never have a knowledge of the world that is not mediated by our senses. You can’t know the external world as in itself it really is. You know the external world by way of perceptual mediation.
"Reid"
Reed responded to Hume in a way that was admirably kind and affirming and rejects this "Copy" or "Idea" theory of Hume and others. He used a thought experiment called the Geometry of Visible.
When we look around us, the light bouncing off objects are projected onto our spherical eyes. Yet, when we look at a drawn square we don't see a spherical projection of the square, but the square itself. For Reed, this contradicts the Copy theory. So as common sense tells us, the external world is knowable