In examining those ingredients which are capable of uniting with love and hatred, I begin to be sensible, in some measure, of a misfortune that has attended every system of philosophy with which the world has been yet acquainted. 'Tis commonly found, that in accounting for the operations of nature by any particular hypothesis, among a number of experiments that quadrate exactly with the principles we would endeavour to establish, there is always some phenomenon which is more stubborn, and will not so easily bend to our purpose. We need not be surprised that this should happen in natural philosophy. The essence and composition of external bodies are so obscure, that we must necessarily, in our reasonings, or rather conjectures concerning them, involve ourselves in contradictions and absurdities. But as the perceptions of the mind are perfectly known, and I have used all imaginable caution in forming conclusions concerning them, I have always hoped to keep clear of those contradictions which have attended every other system. Accordingly, the difficulty which I have at present in my eye is no wise contrary to my system, but only departs a little from that simplicity which has been hitherto its principal force and beauty. The passions of love and hatred are always followed by, or rather conjoined with, benevolence and anger. 'Tis this conjunction which chiefly distinguishes these affections from pride and humility. For pride and humility are pure emotions in the soul, unattended with any desire, and not immediately exciting us to action. But love and hatred are not completed within themselves, nor rest in that emotion which they produce, but carry the mind to something farther. Love is always followed by a desire of the happiness of the person beloved, and an aversion to his misery: as hatred produces a desire of the misery, and an aversion to the happiness of the person hated. So remarkable a difference betwixt these two sets of passions of pride and humility, love and hatred, which in so many other particulars correspond to each other, merits our attention. The conjunction of this desire and aversion with love and hatred may be accounted for by two different hypotheses. The first is, that love and hatred have not only a _cause_ which excites them, viz. pleasure and pain, and an _object_ to which they are directed, viz. a person or thinking being, but likewise an _end_ which they endeavour to attain, viz. the happiness or misery of the person beloved or hated; all which views, mixing together, make only one passion. According to this system, love is nothing but the desire of happiness to another person, and hatred that of misery. The desire and aversion constitute the very nature of love and hatred. They are not only inseparable, but the same.