Psychologia Empirica

We offer this warning for more than one reason. For it is useful for this purpose, lest anyone who is in fact highly unequal to this labor should deem himself equal to it, about to undertake such a great task with vain success. Furthermore, from this we understand why psychology has hitherto been virtually neglected and little cultivated. Finally, we are taught that ontological notions contribute the greatest assistance toward discovering psychological notions, just as we showed in the Horis subsecivis (1729, Spring Quarter, no. 4, § 2 et seqq.) that they serve as guides in eliciting universal notions.

The use of empirical psychology in rational psychology.Empirical psychology provides principles for rational psychology. For in rational psychology, an account must be given of those things which occur in our soul (§. 58, 31 Disc. prælim.). Yet in empirical psychology, the principles are established from which an account is given of those things which occur in the human soul (§. 1). Therefore, empirical psychology provides principles for rational psychology.

Hence, we have already warned elsewhere (note to §. 111, Disc. prælim.) that empirical psychology corresponds to experimental physics. For it is evident that experimental physics also provides principles for dogmatic physics. Therefore, just as he who has a true knowledge of natural things at heart must devote tireless labor to experimental physics, so also he who desires certain knowledge of the soul must necessarily be assiduous in empirical psychology. Indeed, it will become evident in our progress that more can be known with certainty about the human soul than is commonly supposed, if empirical psychology is rightly cultivated.

A second use.Empirical psychology serves to examine and confirm those things which are derived a priori concerning the human soul. For since those things are handed down in empirical psychology which are known by directing attention to those things which occur in our soul while we are conscious of them (§. 2), if any things have been derived a priori concerning the human soul, they must be compared with those things which are established through experience in empirical psychology. For if they are the same as, or agree with, them, it cannot be doubted that they are consistent with the truth; but if they are repugnant to them, it is manifest that they depart from the truth.