«Experience has taught me that those who are utterly Cartesian are scarcely capable of discovery; they merely take on the role of interpreters of or commentators on their master, as the Scholastic philosophers did with Aristotle. And of the many wonderful discoveries since Descartes, I do not know of any which comes from a true Cartesian. (…)
Descartes himself had a rather limited mind. He excelled in speculations over all men, but discovered nothing useful for the life which falls under the senses and which serves in the practice of the arts. All his meditations were either too abstract, such as his metaphysics and geometry, or too fanciful, such as his principles of natural philosophy. (…)
Nevertheless I recognize that what Descartes said about the magnet, the ebb and flow of the sea, and meteors, is utterly ingenious, and surpasses everything the ancients said about these things.»
– Leibniz, Letter on Cartesianism, 1679.