NA TURE. 97 2. Nature. What guarantee have we for the existence of^material o bjects af ferting our sen5j;es ? That the ideas of sense do not come from ourseh es, is shown by the fact that it is not in our power to determine the objects which we perceive, or the character of our perception of them. The supposition that God has caused our perceptions directly,(^or by means of something which has no resemblance whatever to an ex- ternal object extended in three dimensions and movable) is excluded by the fact that God is not a deceiver. In reliance on God's veracity we may accept as true whatever the reason declares concerning body, though not all the reports of the senses, which so often deceive us. At the instance of the senses we clearly and distinctly perceive matter distinct from our mind and from God, extended in three dimensions, length, breadth, and depth, with variously formed and vari- ously moving parts, which occasion in us sensations of many kinds. The belief that perception makes known things as they really are is a prejudice of sense to be dis- carded ; on the contrary, it merely informs us concerning the utility or harmfulness of objects, concerning their rela- tion to man as a being composed of soul and body. (The body is that material thing which is very intimately joined with the mind, and occasions in the latter certain feelings, e.g., pain, which as merely cogitative it would not have.) Sense qualities, as color, sound, odor, cannot constitute the essence of matter, for their variation or loss changes nothing in it ; I can abstract from them without the material thing disappearing.* There is one property, however, extensive magnitude {gumititas), whose removal would imply the de- struction of matter itself. Thus I perceive by pure thought that the essence of matter consists in extension, in that which constitutes the object of geometry, in that magnitude which is divisible, figurable, and movable. This thesis {corpus = extensio sive spatmiit) is next defended by Descartes against several objections. In reply to the objection drawn
- They are merely subjective states in the perceiver, and entirely unlike the
motions which give rise to them, although there is a certain agreement, as the differences and variations in sensation are paralleled by those in the object.
