Principles can be known in two ways. One is by confused knowledge, as when terms are apprehended through the senses and experience, and this suffices for scientific knowledge of the terms in any special science, as in [knowing] that a line has length, while being ignorant of whether its quiddity is substance, quantity or quality, etc. Another way principles can be known is by distinct knowledge, knowing to what category their quiddity pertains, with definitions of terms known distinctly from the evidence of the terms themselves, and this happens through the science of metaphysics through division and composition. And in this way all sciences can be called subordinate, namely to metaphysics. And therefore, given the science of metaphysics, principles of any science whatsoever are known more perfectly than they are suited by nature to be known in that science through its own proper principles. And as a consequence, another science is known more perfectly if one knows metaphysics.
- Scotus, Reportatio I-A, Prol. Q. 2, trans. Wolter and Bychkov