Naturalism is for all effective purposes the same as materialism. The latter – far from the negative connotation that it has acquired because of its spurious relationship with Marxism – is the idea that existence is entirely physical (i.e., there is no metaphysical world). Therefore, all our sensations, including the mental processes through which we acquire knowledge, are based on physical properties of our brains (with all the powers and shortcomings that this implies).
