"In order to understand the world and function in it, we have to categorize, in ways that make sense to us, the things and experiences that we encounter." (#60 2778)

"there are natural dimensions to our categories for objects: perceptual, based on the conception of the object by means of our sensory apparatus; motor activity, based on the nature of motor interactions with objects; functional, based on our conception of the functions of the object; and purposive, based on the uses we can make of an object in a given situation." (#60 2781)

"since the natural dimensions of categories (perceptual, functional, etc.) arise out of our interactions with the world, the properties given by those dimensions are not properties of objects in themselves but are, rather, interactional properties, based on the human perceptual apparatus, human conceptions of function, etc. It follows from this that true statements made in terms of human categories typically do not predicate properties of objects in themselves but rather interactional properties that make sense only relative to human functioning." (#60 2802)