Nor is there required such profound knowledge to discover the present imperfect condition of the sciences, but even the rabble without doors may, judge from the noise and clamour, which they hear, that all goes not well within. There is nothing which is not the subject of debate, and in which men of learning are not of contrary opinions. The most trivial question escapes not our controversy, and in the most momentous we are not able to give any certain decision. Disputes are multiplied, as if every thing was uncertain; and these disputes are managed with the greatest warmth, as if every thing was certain. Amidst all this bustle it is not reason, which carries the prize, but eloquence; and no man needs ever despair of gaining proselytes to the most extravagant hypothesis, who has art enough to represent it in any favourable colours. The victory is not gained by the men at arms, who manage the pike and the sword; but by the trumpeters, drummers, and musicians of the army....
Hume's empiricist approach to philosophy places him with John Locke, George Berkeley, Francis Bacon, and Thomas Hobbes as a British Empiricist. Beginning with his A Treatise of Human Nature (1739), Hume strove to create a total naturalistic science of man that examined the psychological basis of human nature. Against rationalists, Hume held that passion rather than reason governs human behaviour. He argued against the existence of innate ideas, postulating that humans can have knowledge only of the objects of experience, and the relations of ideas, calling the rest "nothing but sophistry and illusion", a dichotomy later given the name Hume's fork. He also argued that inductive reasoning, and therefore causality, cannot, ultimately, be justified rationally: our belief in causality and induction instead results from custom, habit, and experience of "Constant conjunction" rather than logic. He denied that humans have an actual conception of the self, positing that we experience only a bundle of sensations, and that the self is nothing more than this bundle of causally-connected perceptions. Hume's compatibilist theory of free will takes causal determinism as fully compatible with human freedom, and has proved extremely influential on subsequent moral philosophy.
Hume was also a sentimentalist who held that ethics are based on emotion or sentiment rather than abstract moral principle, famously proclaiming that "Reason Is and Ought Only to Be the Slave of the Passions". Contemporary scholars view Hume's moral theory as a unique attempt to synthesize the modern sentimentalist moral tradition to which Hume belonged, with the virtue ethics tradition of ancient philosophy, with which Hume concurred in regarding traits of character, rather than acts or their consequences, as ultimately the proper objects of moral evaluation. Hume's moral theory maintained an early commitment to naturalistic explanations of moral phenomena, and is usually taken to have first clearly expounded the is–ought problem, or the idea that a statement of fact alone can never give rise to a normative conclusion of what ought to be done....