For just as physical perception often casts us into error because it represents external objects in a confused and imperfect way (in a confused way when the objects are too far away from us or poorly lighted, and in an imperfect way because it represents to us only their sides facing us), so the understanding, which often has only a confused and imperfect perception of things because they are not sufficiently present to it and because it fails to discover all their parts, causes the will to fall into a great number of errors by yielding too easily to these obscure and imperfect perceptions.