In Book I., Chap. I., Hutcheson states that the aim of Moral Philosophy is to point out the course of action that will best promote the highest happiness and perfection of men, by the light of human nature and to the exclusion of revelation; thus to indicate the rules of conduct that make up the Law of Nature. Happiness, the end of this art, being the state of the mind arising from its several grateful perceptions or modifications, the natural course of the inquiry is to consider the various human powers, perceptions, and actions, and then to compare them so as to find what really constitutes happiness, and how it may be attained. The principles that first display themselves in childhood are the external senses, with some small powers of spontaneous motion, introducing to the mind perceptions of pleasure and pain, which becoming forthwith the object of desire and aversion, are our first notions of natural good and evil. Next to Ideas of Sensation, we acquire Concomitant ideas of Sensation from two or more senses together--number, extension, &c. Ideas of consciousness or reflection, which is another natural power of perception, complete the list of the materials of knowledge; to which, when the powers of judging and reasoning are added, all the main acts of the understanding are given. There are still, however, some finer perceptions, that may be left over until the will is disposed of. Under the head of Will, he notes first the facts of Desire and Aversion, being new motions of the soul, distinct from, though arising out of, sensations, perceptions, and judgments. To these it is common to add Joy and Sorrow, arising in connexion with desire, though they partake more of sensations than of volitions. Acts of the will are _selfish_ or _benevolent_, according as one's own good, or (as often really in fact happens) the good of others is pursued. Two _calm_ natural determinations of the will are to be conceded; the one an invariable constant impulse towards one's own highest perfection and happiness; the other towards the universal happiness of others, when the whole system of beings is regarded without prejudice, and in the absence of the notion that their happiness interferes with our own. There are also _turbulent_ passions and appetites, whose end is their simple gratification; whereupon the violence and uneasiness cease. Some are selfish--hunger, lust, power, fame; some benevolent--pity, gratitude, parental affection, &c.; others may be of either kind--anger, envy, &c. In none of them is there any reference in the mind to the greatest happiness of self or others; and that they stand so often in real opposition to the calm motions, is sufficient proof of their distinct character, _e.g._, the opposition of lust and calm regard for one's highest interest.