T 2.3.4.2

'Tis a remarkable property of human nature, that any emotion, which attends a passion, is easily converted into it, tho' in their natures they be originally different from, and even contrary to each other. 'Tis true; in order to make a perfect union among passions, there is always requir'd a double relation of impressions and ideas; nor is one relation sufficient for that purpose. But tho' this be confirm'd by undoubted experience, we must understand it with its proper limitations, and must regard the double |relation, as requisite only to make one passion produce another. When two passions are already produc'd by their separate causes, and are both present in the mind, they readily mingle and unite, tho' they have but one relation, and sometimes without any. The predominant passion swallows up the inferior, and converts it into itself. The spirits, when once excited, easily receive a change in their direction; and 'tis natural to imagine this change will come from the prevailing affection. The connexion is in many respects closer betwixt any two passions, than betwixt any passion and indifference.