In entering the seventeenth century we find a new element upon the sea of controversy. Philosophy of the different schools was in each school striving for ascendency; and if not a direct cause of many of the disputes of this century, it gives a coloring to them. At this time philosophy was represented in the two classes of Peripatetics (followers of Aristotle) and Fire-Philosophers, from their proposition that "the dissolution of bodies by the power of fire is the only way in which the first principles of things can be discerned".
The Peripatetics held the professorships in almost all the places of learning; and held that all who questioned Aristotle were little less criminal than downright heretics; and so there was a lively contest kept up between them and the Fire- Philosophers, or chemists.
But there was a union of the interests of these two, when, about 1640, the Cartesian gauntlet, Cogito, ergo sum (i.e., I think, therefore I am), was thrown into the arena; and they both turned with all their energy against the new philosophy; "not," says Mosheim, "so much for their philosophical system as for the honors, advantages, and profits they derived from it." And, "seconded by the clergy who apprehended that the cause of religion was aimed at and endangered by these philosophical innovations, they made a prodigious noise and left no means unemployed to prevent the downfall of their old system... They not only accused Descartes of the most dangerous and pernicious errors, but went so far, in the extravagance of their malignity, as to bring a charge of atheism against him."
In opposition to Descartes, Gassendi also entered the lists, and this gave rise to yet another school of philosophy, the Mathematical. That of Descartes was called the Metaphysical, or Cartesian, philosophy. As the Peripatetic was the only phi losophy taught in the Lutheran schools, the rise of the new philosophy was a new subject for discussion and opposition there, and gave scope for yet more exercise of the controversial propensity.