A few quotes from this book by Jacob Philipp Spener:
…the study of theology should be carried on not by the strife of disputations but rather by the practice of piety.
(Dr. David Chytraeus) “Beware! Satan has the intention of detaining you with unnecessary things and thus keeping you from those which are necessary. Once he has gained an opening in you of a hand-breadth, he will force in his whole body together with sacks full of useless questions, as he formerly did in the universities by means of philosophy.” Here we hear that no little damage is done when one tries to be smart and clever without the Scriptures or beyond them. Nor is there want of examples to substantiate this.
When men’s minds are stuffed with such a theology which, while it preserves the foundation of faith from the Scripture, builds on it with so much wood, hay, and stubble of human inquisitiveness that the gold can no longer be seen, it becomes exceedingly difficult to grasp and find pleasure in the real simplicity of Christ and his teaching. This is so because men’s taste becomes accustomed to the more charming things of reason, and after a while the simplicity of Christ and his teaching appears to be tasteless. Such knowledge, which remains without love, “puffs up” (I Cor. 8:1). It leaves man in his love of self; indeed, it fosters and strengthens such love more and more. Subtleties unknown to the Scriptures usually have their origin, in the case of those who introduce them, in a desire to exhibit their sagacity and their superiority over others, to have a great reputation, and to derive benefit therefrom in the world. Moreover, these subtleties are themselves of such a nature that they stimulate, in those who deal with them, not a true fear of God but a thirst for honor and other impulses which are unbecoming a true Christian. When people are practiced in such things they begin to have great illusions and introduce them at once into the church of Christ, even if they know little or nothing of the one thing needful, which they hold in little esteem. They can hardly be kept from taking to market what gives them the most pleasure, and they generally concentrate on something that is not very edifying to their hearers who are seeking salvation. When they really achieve the purpose they set themselves, they succeed in giving those of their hearers who have ready minds a fair knowledge of religious controversies, and these hearers regard it as the greatest honor to dispute with others. Both preachers and hearers confine themselves to the notion that the one thing needful is the assertion and retention of pure doctrine, which must not be overthrown by errors, even if it is very much obscured with human perversions.