There are unquestionably _two_ sorts of abstraction: 1. "_Comparative_ abstraction, operating upon several real objects, and seizing their resemblances in order to form an abstract idea, which is collective and mediate; collective, because different individuals concur in its formation; mediate, because it requires several intermediate operations." This is the method of the physical sciences, which comprises comparison, abstraction, and generalization. The result in this process is the attainment of a _general_ truth. 2. "_Immediate_ abstraction, not comparative; operating not upon several concretes, but upon a single one, eliminating and neglecting its individual and variable part, and disengaging the absolute part, which it raises at once to its pure form." The parts to be eliminated in a concrete cognition are, first, the quality of the object, and the circumstances under which the absolute unfolds itself; and secondly, the quality of the subject, which perceives but does not constitute it. The phenomena of the me and the not-me being eliminated, the absolute remains. This is the process of rational psychology, and the result obtained is a _universal_ and _necessary_ truth. "Let us take, as an example, the principle of cause. To be able to say that the event I see must have a cause, it is not indispensable to have seen several events succeed each other. The principle which compels me to pronounce this judgment is already complete in the first as in the last event; it can not change in respect to its object, it can not change in itself; it neither increases nor decreases with the greater or less number of applications. The only difference that it is subject to in regard to us is that we apply it, whether we remark it or not, whether we disengage it or not from its particular application. The question is not to eliminate the particularity of the phenomenon wherein it appears to us, whether it be the fall of a leaf or the murder of a man, in order immediately to conceive, in a general and abstract manner, the necessity of a cause for every event that begins to exist. Here it is not because I am the same, or have been affected in the same manner in several different cases, that I have come to this general and abstract conception. A leaf falls; at the same moment I think, I believe, I declare that this falling of the leaf must have a cause. A man has been killed; at the same instant I believe, I proclaim that this death must have a cause. Each one of these facts contains particular and variable circumstances, and something universal and necessary, to wit, both of them can not but have a cause. Now I am perfectly able to disengage the universal from the particular in regard to the first fact as well as in regard to the second fact, for the universal is in the first quite as well as in the second. In fact, if the principle of causality is not universal in the first fact, neither will it be in the