This principle is based upon a distinction between "positive" and "negative" thought, which is made with an air of wonderful precision and accuracy in "the Alphabet of Human Thought."[333] "Thinking is _positive_ when existence is predicated of an object." "Thinking is _negative_ when existence is not attributed to an object." "Negative thinking," therefore, is not the thinking of an object as devoid of this or that particular attribute, but as devoid of all attributes, and thus of all existence; that is, it is "the negation of all thought"--_nothing_. "When we think a thing, that is done by conceiving it as possessed of certain modes of being or qualities, _and the sum of these qualities constitutes its concept or notion_." "When we perform an act of negative thought, this is done by thinking _something_ as _not_ existing in this or that determinate mode; and when we think it as existing in no determinate mode, _we cease to think at all--it becomes a nothing_."[334] Now the Infinite, according to Hamilton, can not be thought in any determinate mode; therefore we do not think it at all, and therefore it is for us "a logical Non-entity." [Footnote 333: "Discussions," Appendix I. p. 567.] [Footnote 334: "Logic," pp. 54, 55.] It is barely conceivable that Hamilton might imagine himself possessed of this singular power of "performing an act of negative thought"--that is, of thinking and not thinking at once, or of "thinking something" that "becomes nothing;" we are not conscious of any such power. To think without an object of thought, or to think of something without any qualities, or to think "something" which in the act of thought melts away into "nothing," is an absurdity and a contradiction. We can not think about nothing. All thought must have an object, and every object must have some predicate. Even space has some predicates--as receptivity, unity, and infinity. Thought can only be realized by thinking something existing, and existing in a determinate manner; and when we cease to think something having predicates, we cease to think at all. This is emphatically asserted by Hamilton himself.[335] "Negative thinking" is, therefore, a meaningless phrase, a contradiction in terms; it is no thought at all. We are cautioned, however, against regarding "the negation of thought" as "a negation of all mental ability." It is, we are told, "an attempt to think, and a failure in the attempt." An attempt to think about _what_? Surely it must be about some object, and an object which is _known_ by some sign, else there can be no thought. Let any one make the attempt to think without something to think about, and he will find that both the process and the result are blank nothingness. All thought, therefore, as Calderwood has amply shown, is, must be, _positive_. "Thought is nothing else than the comparison of objects known; and as knowledge is always positive, so must our thought be. All knowledge implies an object _known_; and so all thought involves