Yet it can scarcely be necessary for me to point out to you, in so many terms, that what we call theology, if true, is a science; and if false, is not theology; or that the distinction even between natural science and theology is illogical: for you might distinguish indeed between natural and unnatural science, but not between natural and spiritual, unless you had determined first that a spirit had no nature. You will find the facts to be, that entirely true knowledge is both possible and necessary--first of facts relating to matter, and then of the forces and passions that act on or in matter;--that, of all these forces, the noblest we can know is the energy which either imagines, or perceives, the existence of a living power greater than its own; and that the study of the relations which exist between this energy, and the resultant action of men, are as much subjects of pure science as the curve of a projectile. The effect, for instance, upon your temper, intellect, and conduct during the day, of your going to chapel with or without belief in the efficacy of prayer, is just as much a subject of definite science, as the effect of your breakfast on the coats of your stomach. Which is the higher knowledge, I have, with confidence, told you; and am not afraid of any test to which you may submit my assertion. 68. Assuming such limitation, then, and such rank, for our knowledge; assuming, also, what I have now, perhaps to your weariness, told you, that graphic art is the shadow, or image, of knowledge,--I wish to point out to you to-day the function, with respect to both, of the virtue called by the Greeks 'σωφροσύνη' 'safeness of mind,' corresponding to the 'salus' or 'sanitas' mentis, of the Latins; 'health of heart' is, perhaps, the best English; if we receive the words 'mens,' 'μῆνις,' or 'φρήν,' as expressing the passionate soul of the human being, distinguished from the intellectual; the 'mens sana' being possible to all of us, though the contemplative range of height her wisdom may be above our capacities; so that to each of us Heaven only permits the ambition of being σοφός, but commands the resolution to be σώφρων.