Anatomy and Physiology, through their effects on the practice of medicine and hygiene, modify our actions almost as much as does our acquaintance with the evils and benefits which common environing agencies may produce on our bodies. All Science is prevision; and all prevision ultimately aids us in greater or less degree to achieve the good and avoid the bad. As certainly as the perception of an object lying in our path warns us against stumbling over it; so certainly do those more complicated and subtle perceptions which constitute Science, warn us against stumbling over intervening obstacles in the pursuit of our distant ends. Thus being one in origin and function, the simplest forms of cognition and the most complex must be dealt with alike. We are bound in consistency to receive the widest knowledge which our faculties can reach, or to reject along with it that narrow knowledge possessed by all. There is no logical alternative between accepting our intelligence in its entirety, or repudiating even that lowest intelligence which we possess in common with brutes. To ask the question which more immediately concerns our argument—whether Science is substantially true?—is much like asking whether the sun gives light. And it is because they are conscious how undeniably valid are most of its propositions, that the theological party regard Science with so much secret alarm. They know that during the two thousand years of its growth, some of its larger divisions—mathematics, physics, astronomy—have been subject to the rigorous criticism of successive generations; and have notwithstanding become ever more firmly established. They know that, unlike many of their own doctrines, which were once universally received but have age by age been more frequently called in question, the doctrines of Science, at first confined to a few scattered inquirers, have been slowly growing into general acceptance, and are now in great part admitted as beyond dispute. They know that men of science throughout the world subject each other’s results to the most searching examination; and that error is mercilessly exposed and rejected as soon as discovered. And, finally, they know that still more conclusive testimony is to be found in the daily verification of scientific predictions, and in the never-ceasing triumphs of those arts which Science guides.