_Not a distinct Faculty._--The form of mental activity now described, is hardly to be ranked as a distinct faculty of the mind, although it has been not unfrequently so treated by writers on mental science. It enters more or less fully into all mental operations; like consciousness and attention, it is, to some extent, involved in the exercise of all the faculties, and cannot, therefore, be ranked, with propriety, as coördinate with them. It is not confined to the investigations of science, but is an activity constantly exercised by all men. We have in our minds a multitude of general conceptions, the result of previous observation and thought. Every moment some new object presents itself. With the quickness of thought, we find its place among the conceptions already in the mind: it agrees with this, it is incompatible with that, it belongs with the one, it is excluded from the other. This is the form of most of our thinking; indeed, no small part of our mental activity consists in this perception of agreements and disagreements, and in the referring of some particular object of experience, some individual conception, to the class or general conception under which it properly belongs. The expression of such a judgment is a proposition. We think in propositions, which are only judgments mentally expressed. We discourse in propositions, which are judgments orally expressed. We cannot frame a proposition which does not affirm, or deny, or call in question, something of something. _Judgment in relation to Knowledge._--Are judgment and knowledge identical? Is all knowledge only some form of judgment? So Kant, Tissot, and other writers of that school, would affirm. "Judgment is the principal operation of the mind, since it is concerned in all knowledge properly so called." "All our knowledges are judgments. To know, is to distinguish, and to distinguish, is at once to affirm, and to deny." Such was also Dr. Reid's doctrine, in opposition to Locke, who distinguished between knowledge and judgment. Reid, on the contrary, regards knowledge as only one class of judgments, namely, those about which we are most positive and certain. According to this view, judgment seems to cover the whole field of mental activity. Sir William Hamilton thus regards it. We cannot even experience a sensation, he maintains, without the mental affirmation or judgment that we are thus and thus affected.