While engaged in a profound study of the descriptive peculiarities connected with the third fundamental class of psychical states above referred to--a study analogous to that previously undertaken by him with regard to the judgment--Brentano was led to the discovery of the _principles of ethical knowledge_ which form the subject of this lecture. The author, in his lectures delivered before students of all faculties, but especially to students in the faculty of law, during each winter session throughout many years, presented a complete and fully developed system of ethical teaching based upon these principles.[A] Unfortunately, this lecture still remains unpublished. The same holds good of many of his inquiries into “descriptive psychology,” or psychognosie, e.g. inquiries into the nature of sense perceptions according to their qualitative and spatial nature, the nature of the continuum, the time phenomenon, etc., the results of which are hitherto familiar only to those who have either attended his lectures, or have been present during private conversations. [A] Since this essay was written the statements as to the principles here developed have been modified only in respect of two points which, if not practically important, are still theoretically so, and these, with the author’s permission, may be here shortly referred to:-- 1. In the lecture (p. 15) it is said that anything may be either affirmed or denied, and that if the affirmation is right its denial must be considered wrong, and vice versâ. It is also stated that this is true analogously in respect of love and hate. This Brentano no longer asserts, but rather observes that whereas the whole must be denied, if but a part is untrue, a sum of good and bad, on the other hand, may be of such a nature as nevertheless as a whole to be worthy of love. It may be also so constituted that good and bad remain in equilibrium. 2. In the lecture (p. 24), and in the corresponding note 37 (p. 87), it is said that our preference qualified as right in the case where, for instance, to one good another is added, is drawn, not from our knowledge of the preferability of the sum as opposed to the parts, but that analytic judgments here yield the means of our advance in knowledge, and that the corresponding preferences are therefore qualified as right, since the knowledge (given analytically) is here the criterion. Here it is overlooked that without the experience of acts of preferring we neither have nor could have the conception, and therefore also our notion of preferability. And so it is also true that it is by no means evident from analysis that one good plus another is preferable to each of these goods taken singly. Here also a complete analogy to the sphere of the true is wanting.