INTRODUCTION TO PSYCHOLOGY.

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Indeed, if we assume that Rational Psychology is a science—a point that will soon be proven—it must also be granted that there is a place within it for formal demonstration. Certainly, when you rest content only with those things known about the soul a posteriori original: "a posteriori." This refers to knowledge gained from observation and experience after the fact, rather than through pure reason., you are resting in Empirical Psychology The study of the soul through observation and experimental data., which we have recently set forth in its own specific volume. In such a case, you do not progress to Rational Psychology The study of the soul through logical deduction and the "mathematical method" of proof., but rather overlook it; consequently, you neglect to fulfill all the duties of a Philosopher, whose task it is to provide a reason for those things which exist (§. 46. Preliminary Discourse). Therefore, we, whose intention is to transmit a complete system of philosophy, must strive to the best of our ability to present the sequence of those demonstrations which have been desired until now, intending to supply the deficiency with which this most noble part of philosophy still struggles, as far as is possible.

From where the principles of demonstration are to be sought.

In Rational Psychology, the principles of demonstration are to be sought from Ontology, Cosmology, and Empirical Psychology. In the list of principles of demonstration The foundational truths, such as axioms and definitions, used to build a logical argument., nothing is accepted except for definitions, indubitable experiences, axioms, and propositions that have already been demonstrated (§. 562. Ontology). But Empirical Psychology provides the definitions of those things pertaining to the soul, as is clear from the treatment of that subject, and it establishes principles made manifest through experience (§. 1. Empirical Psychology). Therefore, in Rational Psychology, the principles of demonstration must be sought from Empirical Psychology. This was the first point.

Furthermore, since the human soul actually exists (§. 20. Empirical Psychology), it is numbered among beings original: "entium," referring to anything that exists or is possible. (§. 134. Ontology); consequently, those things which have been demonstrated concerning being in general can be applied to the soul as a specific kind of being (§. 360. 361. Empirical Psychology). For this reason, since those things which ought to be stated about being in general are demonstrated in Ontology The branch of metaphysics dealing with the nature of existence and being. (§. 1. Ontology), the principles of demonstration in Rational Psychology are also sought from Ontology. This was the second point.

Finally, the soul perceives the changes of bodies through the sen- The word is completed on the following page as "sensory organs."