Rationalism

RATIONALISM is that trend of philosophy which inter cedes for the rights of "natural reason" and sees in it the source of all truth. Common to all the historical forms of rationalism is the belief in the "autonomy of thought," i.e., the view that thought can discover by its own strength, without support from a supernatural revelation and without appeal to sense perception, a system of "eternal truths," a system presented to thought within its own realm and comprehended by thought as necessary.

In the theoretical field there are certain "innate ideas" which form the basis of all certainty and from which all specific proofs are derivable by logical inference. The same is true also of prac tical consciousness. Beside the theoretical, especially logical and mathematical, truths, there are ethical truths which can be com prehended with certainty as unconditional obligations or impera tives of action.

Early History.—This fundamental conviction found its clear est expression in the Stoic doctrine of the Kowai. gvvotac (no titiae communes), as it is developed in the writings of Cicero. From here it exercised a lasting influence. In modern philosophy this influence first appears within the religious sphere, in which also the terms "rationalism" and "rationalist" seem to have orig inated, and where they designate the assumption that there cannot be an insurmountable conflict between the "natural" cog nition of reason and the "supernatural" truth of revelation.

Thus, in English religious philosophy of the 16th and 17th cen turies, for instance, those are called "rationalists" who consider reason the highest authority not only in science but also in mat ters relating to religion and society. (Cf. Lechler, Geschichte des englisc/ien Deismus, p. 61.) Also in the Netherlands it was cus tomary at that period to distinguish between "rational" and "non rational" theologians. (Cf. Bayle, Dictionnaire historique et critique.) In the introduction to his Thoodicee, in the "Discours de la conformite de la foi avec la raison," Leibniz gave an outline of the development and significance of "theological rationalism." It was especially in England and through Herbert of Cher bury (1581-1648) that religious rationalism received its complete foundation and its clear formulation. In his two works De veritate (1624) and De religiose gentiliurn Herbert of Cherbury starts from the assumption that reason possesses in itself the capacity for all truths, including religious and moral ones. Beside reason, there is no other higher authority; for even revelation can claim validity only because its content har monizes with the principles of rational knowledge. The dogma of original sin, or the corruption of reason through the fall of man, is unconditionally rejected by Herbert. In every healthy

and reasonable person there are universal and innate truths, by which our earthly mind, implanted as it were, from heaven, is enabled to participate in the recognition of things of God and of moral good. From the sphere of religion this doctrine passes to the science of law (doctrine of "natural law") ; to the theory of the State (doctrine of "raison d'etat," of the foundations of international law, etc.), to ethics ("autonomy" of morals). In its totality it represents the new "natural system of the sciences of mind" which, since the Renaissance, unfolds itself steadily and supercedes the mediaeval view of the world, which was theo logical and hierarchic.

Modern Science.

The strongest support was given to this movement by the new achievements of natural knowledge through the great scientists of the 17th century, Copernicus, Galilei, Kepler and Descartes. The new science rests on the basis of mathe matics, and it recognizes as "clear and distinct" only what can be expressed in mathematical form. All such cognitions have this in common : that they go back to certain major premises, to "axioms" and "principles" which can be comprehended by reason as universal and necessary, as a priori propositions. Thus, ac cording to Galilei, Truth is written in the great book of Nature, but only he can read it who can decipher the letters in which it is written. These letters, however, are the terms of mathematics, especially of geometry : the concepts of the straight line, the circle, the sphere, etc. None of these concepts is derived from experience; the mind rather takes them "from itself" in order to apply them to sense-perceptions. In the same way, Kepler considers the ideas of number and magnitude as "innate ideas," not drawn from experience but required for the scientific investi gation of nature. (Cf. Cassirer, Des Erkenntnisproblem, 3rd ed., I., p. 328 sqq.) Descartes enlarges this view by setting forth a system of universal concepts of reason which are obtained by mental analysis from a contemplation of certain fundamental, logical and mathematical, relationships, and which can be applied to all empirical data. These concepts are valid—as he expounds in Le monde—not alone for the actual world but for all possible worlds, so that, in understanding by means of them every effect from its cause, we can obtain a priori knowledge of the universe as a whole. As instances of such fundamental concepts, Descartes cites primarily the concept of Being, then also the ideas of Num ber and Time, of Space, Figure and Motion (Oeuvres, ed. Adam Tannery, III., 665).