This makes logical sense, for the only way to perceive this real essence would be to become the object itself! Although the idea is logical, it does contain a certain grounding for agnosticism. Let the reader consider this: if there is no way to actually sense the true material essence of anything, and all knowledge in empiricism comes from the senses, then the real material essence can not be perceived and therefore it can not be posited. This deserves careful consideration, for thematerialist has been self-proclaimed a skeptic! If the believer in this theory were asked if a mythical beast such as a cyclops existed he would most certainly say no. As part of his reply he might add that because it can not be sensed it is not a piece of knowledge. After being enlightened by the above proposed argument, though, that same materialist is logically forced to agree that, because the "material substratum1" itself can not be sensed, its existence can not be treated as knowledge. The materialist belief has, in effect, become as futile as proving that the cyclops exists; his ideas have lead him into skepticism.Having proven that the materialist is, at best, a doubter, Berkeley goes on to offer the compelling argument that primary andsecondary qualities are, together, one thing. As the materialist believes, primary qualities of an object are those things that areabstract (not sense oriented). Examples of these would be number, figure, motion, and extension. Secondary qualities are those things that are concrete (sense oriented), such as color, smell, sound, and taste. The materialist feels that these primary qualities persist even when the secondary ones are not there. Thus, if a person were blind, then that individual would not be able to hear or to touch items; yet the so-called real qualities such as figure would remain existent in the objects. As previously shown, the materialist is agnostic in his belief of these real (primary) qualities.