And as the relations of magnitude, as they are the objects of our reason, are only the objects of its assent or dissent; so good and evil, as they are objects of our reason, are only the objects of its _desire_ or _aversion_: and as the assent or dissent, in matters of speculation, whether right or wrong, is solely the act of our reason; so desire or aversion, in human life, whether right or wrong, is equally the act of our reason. We often say, that our passions deceive us, or persuade us; but this is no more strictly so, than when we say, our _interest_ deceived, or a bribe blinded us. For bribes and interest are not active principles, nor have any power of deception; it is only our reason that gives them a false value, and prefers them to a greater good. It is just so in what we call the deceit of our passions: they meddle with us no more than bribes meddle with us; but that pleasurable perception, which is to be found in certain enjoyments, is by our reason preferred to that better good, which we might expect from self-denial. We say again, that our passions paint things in false colours, and present to our minds vain appearances of happiness. But this is no more strictly true, than when we say, ♦our _imagination_ forms castles in the air. For the imagination signifies no distinct faculty from our reason, but only reason acting upon our _own ideas_. ♦ “out” replaced with “our” So when our passions are said to give false colours to things, or present vain appearances of happiness, it is only our reason acting upon its own ideas of _good_ and _evil_, just as it acts upon its own ideas of _architecture_, in forming castles in the air. So that all _that_ which we call different faculties, tempers, and passions, strictly speaking, means nothing else, but the various acts of one and the same rational principle, which has different names, according to the objects that it acts upon, and the manner of its acting. In some things it is called speculative, in others it is called practical reason. And we may as justly think our speculative reason is a different faculty from our practical reason, as that our aversions, or likings, are not as fully to be ascribed to our reason, as syllogisms and demonstrations.