In one very important respect, however, the inquiries, relating to the physiology of mind, differ from those which relate to the physiology of our animal frame. If we could render ourselves acquainted with the intimate structure of our bodily organs, and all the changes which take place, in the exercise of their various functions, our labour, with respect to them, might be said to terminate. But though our intellectual analysis were perfect, so that we could distinguish, in our most complex thought or emotion, its constituent elements, and trace with exactness the series of simpler thoughts which have progressively given rise to them, other inquiries, equally, or still more important, would remain. We do not know all which is to be known of the mind, when we know all its phenomena, as we know all which can be known of matter, when we know the appearances which it presents, in every situation in which it is possible to place it, and the manner in which it then acts or is acted upon by other bodies. When we know that man has certain affections and passions, there still remains the great inquiry, as to the propriety or impropriety of those passions, and of the conduct to which they lead. We have to consider, not merely how he is capable of acting, but also, whether, acting in the manner supposed, he would be fulfilling a duty or perpetrating a crime. Every enjoyment which man can confer on man, and every evil, which he can reciprocally inflict or suffer, thus become objects of two sciences--first of that intellectual analysis which traces the happiness and misery, in their various forms and sequence, as mere phenomena or states of the substance _mind_;--and secondly, of that ethereal judgment, which measures our approbation and disapprobation, estimating, with more than judicial scrutiny, not merely what is done, but what is scarcely thought in secrecy and silence, and discriminating some element of moral good or evil, in all the physical good and evil, which it is in our feeble power to execute, or in our still frailer heart, to conceive and desire. To this second department of inquiry belong the doctrines of general _ethics_.