(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.%

Christian Wolff was born at Breslau in 1679, studied theology at Jena, and
in addition mathematics and philosophy, habilitated at Leipsic in 1703,
and obtained, through the instrumentality of Leibnitz, a professorship of
mathematics at Halle, in 1706. His lectures, which soon extended themselves
over all philosophical disciplines, met with