Hobbes’s Materialism Notes for September 27

Main points

We started with the medieval view of perception that both Descartes and Hobbes rejected. Then we noted where Descartes and Hobbes parted company. Hobbes was a materialist, meaning just what you think it does, while Descartes was a dualist, meaning that he thought the mind was “really distinct” from the material body and brain.

We finished by discussing three points about knowledge: Hobbes’s criticism of Descartes’s dream argument, the different conceptions of knowledge in Descartes’s and Hobbes’s philosophies, and Hobbes’s reasons for caring about ghosts and spirits.

The handout covers the medieval view and singles out a few passages from Descartes.


Descartes’s project was to provide a foundation for the sciences. The foundation would be beliefs that are known with certainty. In the Meditations, he imposes a fairly strict standard for knowledge. To know that there is a mug of coffee over there, I have to be certain that there is a mug of coffee over there. Among other things, that means that I could tell the difference between:

  1. There really is a mug of coffee over there and I see it.
  2. There appears to be a mug of coffee over there. All my senses tell me that it is there even though it isn’t really there.

Hobbes doesn’t talk about knowledge. But he seems quite satisfied with proofs that are less than certain. Look at his reasons for believing that he can tell he isn’t dreaming when he’s awake. Those don’t establish certainty. But they are all that a sane person would need.

More broadly, he offers up his materialist explanation of how objects cause perceptions in minds without pausing to ask how he knows that there really are such things as objects. And he conceded that our ideas, which he thought were motions in our heads, don’t necessarily resemble external objects! I believe he thought that was the best explanation of how sense perception works, whether it could be established with certainty or not.

I think that they both have a point. On the one hand, I think that knowledge really does have to involve something like certainty. On the other hand, I think that the pursuit of certainty would be crazy. The useful kind of knowledge is almost always uncertain. So I need to decide what my philosophy of knowledge is, or, to use a fancy term, what I believe about ‘epistemology’, the study of knowledge.

This page was written by Michael Green for The Image of God, ID-1, Fall 2007. It was posted September 28, 2007.
The Image of God