In the absence of a science of optics, sensible people were especially wary of “optical illusions” (deceptiones visus). This medieval distrust of all optical devices was the great obstacle to a science of optics. As we have seen, it was believed that any device standing between the senses and the object to be sensed could only mislead the God-given faculties. And to a certain extent the crude microscopes in those days confirmed their suspicions. Chromatic and spherical aberration still produced fuzzy images.
