The preceding Lectures, Gentlemen, have, I trust, sufficiently convinced you of the _importance_ of the science on which we are to enter,--if, indeed, many of the advantages which we have considered were not of themselves so obvious, as readily to have occurred to your own reflection, or at least to require less illustration, than,--in my desire to interest not your attention merely, but your zealous ardour, in a science which appears to me so truly to deserve it,--I have thought necessary to give them. We have seen, how interesting the mind is, as an object of study, _from its own intrinsic excellence_, even though it were to be considered in no other light, than as a mere part of the universal system of things, necessary, therefore, to be comprehended with every other existing substance, _in a system of general physics_. We have seen, likewise, in how many important respects, the study of the science of Mind is favourable to the growth of virtuous sentiment, and to the refinement and happiness of society; and, above all, how essential an acquaintance with it is, to the proper conduct of our inquiries,--not merely in those sciences, the objects of which are kindred or analogous, but in every other science, the various objects of which, however independent, and even remote from it they may seem, must always be considered, not as they exist in _themselves_, but as they exist in _relation to it_; since they can be known to us only through the medium of the mental affections, or feelings, excited by them, which have laws peculiar to themselves, and analyzed and arranged only by our mental faculties, which have their own peculiar limits of extent and power.