§ 131. Having advanced the direct empiricist argument for phenomenalism, Berkeley now gives the rationalistic motive an opportunity to express itself in the queries of Hylas as to whether there be not an "absolute extension," somehow abstracted by thought from the relativities of perception. Is there not at least a _conceivable_ world independent of perception? The answers of Philonous throw much light upon the Berkeleyan position. He admits that thought is capable of separating the primary from the secondary qualities in certain _operations_, but at the same time denies that this is forming an idea of them as separate. "I acknowledge, Hylas, it is not difficult to form general propositions and reasonings about those qualities, without mentioning any other; and, in this sense, to consider or treat of them abstractedly. But, how doth it follow that, because I can pronounce the word _motion_ by itself, I can form the idea of it in my mind exclusive of body? or, because theorems may be made of extension and figures, without any mention of _great_ or _small_, or any other sensible mode or quality, that therefore it is possible such an abstract idea of extension, without any particular size or figure, or sensible quality, should be distinctly formed, and apprehended by the mind? Mathematicians treat of quantity, without regarding what other sensible qualities it is attended with, as being altogether indifferent to their demonstrations. But, when laying aside the words, they contemplate the bare ideas, I believe you will find, they are not the pure abstracted ideas of extension."[279:11] Berkeley denies that we have ideas of pure extension or motion, because, although we do actually _deal_ with these and find them intelligible, we can never obtain a state of mind in which they appear as the content. He applies this psychological test because of his adherence to the general empirical postulate that knowledge is limited to the individual content of its own individual states. "It is a universally received maxim," he says, "that _everything which exists is particular_." Now the truth of mathematical reckoning is not particular, but is valid wherever the conditions to which it refers are fulfilled. Mathematical reckoning, if it is to be particular, must be regarded as a particular act or state of some thinker. Its truth must then be construed as relative to the interests of the thinker, as a symbolism which has an instrumental rather than a purely cognitive value. This conclusion cannot be disputed short of a radical stand against the general epistemological principle to which Berkeley is so far true, the principle that the reality which is known in any state of thinking or perceiving is the state itself. [Sidenote: The Transition to Spiritualism.]