Ground is the seat or basis of Being, Mind, Form, Mode, Limitation, Relation, etc. Behind any momented thought, say Sun shines, Mind thinks, or It is, lies, it may be latent, but all potential, the mere thought stripped of all comprehension: Sun, Mind, or It. It is wholly irrelevant that a ground is manifest only by means of its comprehension if it be true that it _must_ be supposed as the seat of that comprehension. Undistributed and therefore unrelated or absolute ground from its very nature admits of no other predicate than mere being. It is in general at once the All and Existence. Its negative or Naught has no ground, being, or comprehension whatever, and no proper denomination, its name being only quasi-denominative and for convenience of notation merely. Form or Thought breaks this barren universe of mere Ground and Being by the formation of modes of Ground and by the more or less arbitrary fiats and finds of Limitation. By the formation of Mode emerge Form, Time, and Extent, and perhaps Cause and Aim. By Limitation emerge Part and Whole, Number, and Relation in all their manifold involutions. Attribute being only _degraded_ Relation, and Quantity being only one _power_ of Relation. It is a most notable peculiarity of thought that it has the ability and that it is its custom to take any form or phase of Being, and regard and deal with it as a ground. Hence every momented thought (which in effect embraces every thought properly speaking) makes two distinct references, its ground reference and its being or predicate reference. This seems to be the bottom truth in respect to the much vexed topic of extension and comprehension. There would seem to be, therefore, in reality only two ultimate categories, Ground and Being. As to how the categories, usually taken as such, and their complements, should be distributed between Ground and Being, would seem to be a matter requiring much pondering to arrange. Owing to the double quality of so many of the mental alternates, as in one regard Being and in another regard Ground, much difficulty might well be anticipated. Neglecting this distribution we may say that very universal terms of thought are Ground, Being, Form, Mode, Limit, Number, Part, Relation. Epoch, Place, Alteration, Event, Cause, Effect, Aim, and the like. The cardinal mental activities which _produce_ thought seem to be, in order, Attention, Conception, Recognition, Induction, and Deduction. In all these operations there is opportunity for not only true, but erroneous thought, and logic in its office as the inspector and judge of thought in respect of its truth or error, should study all these operations and those which are subsidiary to them, and ascertain the causes of error and the means of truth, and perfect methods of deriving truth with certainty and ease.