Psychologia Empirica

(§. 567 Log.). But if that which has been proven a priori concerning the soul is not yet found in empirical psychology, by the benefit of other things which are handed down in empirical psychology, attention must be directed toward our own mind and fixed upon that which ought to correspond to the same, so that it may appear whether it agrees with it or not. And if anything occurs which cannot be reduced to observation, it is permissible to see whether it is the same as that which follows from a principle established in empirical psychology, or whether something established in empirical psychology follows from that which was elicited a priori. Thus it appears that empirical psychology serves for examining and confirming those things which are elicited a priori concerning the human soul.

And in this, empirical psychology again agrees with experimental physics: for we also use experiments as examinations of physical dogmas, or rather [those things] elicited from other experiments, or from these things which were deduced from other experiments. Rational psychology hands down those things which become known a priori concerning the soul (§. 58 Disc. prælim.). Wherefore it is clear that rational psychology promotes the growth of empirical [psychology], even if it borrows principles from it: for it returns with interest what it had borrowed from it. Indeed, it does not seem impossible that those things should be derived a posteriori from observations without the aid of rational psychology; yet we are taught by the very fact that this cannot be done conveniently. Attention to observations is lacking, without which it is not granted to notice what happens in the soul. Truths deduced a priori make us aware of those things which must be observed, and which otherwise escape our thought. The same [truths] suggest a method, without which we cannot be conscious of those things which happen within us. We speak of things experienced, which they also will experience who will devote effort to making familiar to themselves the notions in psychology. The psychologist imitates the Astronomer in this matter, who elicits a theory from observations, and confirms the theory which he has elicited through observations again, and by the aid of the theory is led to observations which otherwise would not have entered his thought at all. And for this reason, in rational psychology, those things are interspersed with demonstrations which ought to be referred to empirical [psychology]. And where empirical psychology is founded, where rational [psychology] is already cultivated, it can be enriched with very many principles, which otherwise [could be found] with difficulty in the same