10.  Argumentum ad HOMINEM.—­They who assert that figure, motion, and the rest of the primary or original qualities do exist without the mind in unthinking substances, do at the same time acknowledge that colours, sounds, heat cold, and suchlike secondary qualities, do not—­which they tell us are sensations existing in the mind alone, that depend on and are occasioned by the different size, texture, and motion of the minute particles of matter.  This they take for an undoubted truth, which they can demonstrate beyond all exception.  Now, if it be certain that those original qualities are inseparably united with the other sensible qualities, and not, even in thought, capable of being abstracted from them, it plainly follows that they exist only in the mind.  But I desire any one to reflect and try whether he can, by any abstraction of thought, conceive the extension and motion of a body without all other sensible qualities.  For my own part, I see evidently that it is not in my power to frame an idea of a body extended and moving, but I must withal give it some colour or other sensible quality which is acknowledged to exist only in the mind.  In short, extension, figure, and motion, abstracted from all other qualities, are inconceivable.  Where therefore the other sensible qualities are, there must these be also, to wit, in the mind and nowhere else.

11.  A second argument ad HOMINEM.—­Again, great and small, swift and slow, are allowed to exist nowhere without the mind, being entirely relative, and changing as the frame or position of the organs of sense varies.  The extension therefore which exists without the mind is neither great nor small, the motion neither swift nor slow, that is, they are nothing at all.  But, say you, they are extension in general, and motion in general:  thus we see how much the tenet of extended movable substances existing without the mind depends on the strange doctrine of abstract ideas.  And here I cannot but remark how nearly the vague and indeterminate description of Matter or corporeal substance, which the modern philosophers are run into by their own principles, resembles that antiquated and so much ridiculed notion of MATERIA Prima, to be met with in Aristotle and his followers.  Without extension solidity cannot be conceived; since therefore it has been shown that extension exists not in an unthinking substance, the same must also be true of solidity.