If Thomasius was the leader of those popular philosophers who, unconcerned about systematic continuity, discussed every question separately before the tribunal of common sense, and found in their lack of allegiance to any philosophical sect a sufficient guarantee of the unprejudicedness and impartiality of their reflections, Count Walter von Tschirnhausen (1651-1708; _Medecina Mentis sive Artis Inveniendi Praecepta Generalia_, 1687), a friend of Spinoza and Leibnitz, became the prototype of another group of the philosophers of the Illumination. This group favored eclecticism of a more scientific kind, by starting from considerations of method and seeking to overcome the antithesis between rationalism and empiricism. While fully persuaded of the validity and necessity of the mathematical method in philosophical investigations, as well as elsewhere, Tschirnhausen still holds it indispensable that the deductions, on the one hand, start from empirical facts, and, on the other, that they be confirmed by experiments. Inner experience gives us four primal facts, of which the chief is the certainty of self-consciousness. The second, that many things affect us agreeably and many disagreeably, is the basis of morals; the third, that some things are comprehensible to us and others not, the basis of logic; the fourth, that through the senses we passively receive impressions from without, the basis of the empirical sciences, in particular, of physics. Consequently consciousness, will, understanding, and sensuous representation _(imaginatio)_, together with corporeality, are our fundamental concepts. Not perception _(perceptio)_, but conception _(conceptio)_ alone gives science; that which we can "conceive" is true; the understanding as such cannot err, but undoubtedly the imagination can lead us to confuse the merely perceived with that which is conceived. The method of science is geometrical demonstration, which starts from (genetic) definitions, and from their analysis obtains axioms, from their combination, theorems. That which is thus proved _a priori_ must, as already remarked, be confirmed _a posteriori_. The highest of all sciences is natural philosophy, since it considers not sense-objects only, not (like mathematics) the objects of reason only, but the actual itself in its true character. Hence it is the divine science, while the human sciences busy themselves only with our ideas or the relations of things to us. %2. Christian Wolff.%