If physical causes influence morals in the manner we have described, may they not also influence religious principles and opinions? I answer in the affirmative; and I have authority, from the records of physic, as well as from my own observations, to declare, that religious melancholy and madness, in all their variety of species, yield with more facility to medicine, than simply to polemical discourses, or to casuistical advice. But this subject is foreign to the business of the present inquiry. From a review of our subject, we are led to contemplate with admiration, the curious structure of the human mind. How distinct are the number, and yet how united! How subordinate, and yet how co-equal are all its faculties! How wonderful is the action of the mind upon the body! of the body upon the mind! and of the Divine Spirit upon both! What a mystery is the mind of man to itself!---- O! Nature!---- or, to speak more properly, O! THOU GOD OF NATURE! in vain do we attempt to scan THY immensity, or to comprehend THY various modes of existence, when a single particle of light, issued from THYSELF, and kindled into intelligence in the bosom of man, thus dazzles and confounds our understandings! The extent of the moral powers and habits in man is unknown. It is not improbable, but the human mind contains principles of virtue, which have never yet been excited into action. We behold with surprise the versatility of the human body in the exploits of tumblers and rope-dancers. Even the agility of a wild beast has been demonstrated in a girl of France, and an amphibious nature has been discovered in the human species, in a young man in Spain. We listen with astonishment to the accounts of the _memories_ of Mithridates, Cyrus, and Servin. We feel a veneration bordering upon divine homage, in contemplating the stupenduous _understandings_ of lord Verulam and sir Isaac Newton; and our eyes grow dim, in attempting to pursue Shakespeare and Milton in their immeasurable flights of _imagination_. And if the history of mankind does not furnish similar instances of the versatility and perfection of our species in virtue, it is because the moral faculty has been the subject of less culture and fewer experiments than the body, and the intellectual faculties of the mind. From what has been said, the reason of this is obvious. Hitherto the cultivation of the moral faculty has been the business of parents, schoolmasters, and divines[14]. But if the principles, we have laid down, be just, the improvement and extension of this principle should be equally the business of the legislator, the natural philosopher, and the physician; and a physical regimen should as necessarily accompany a moral precept, as directions with respect to the air, exercise, and diet, generally accompany prescriptions for the consumption, and the gout. To encourage us to undertake experiments for the improvement of morals, let us recollect the success of philosophy in lessening the number,