288. With the first of the above questions Hume only concerns himself so far as to show that we cannot know either intuitively or demonstratively, in Locke’s sense of the words, that ‘everything whose existence has a beginning also has a cause.’ Locke’s own argument for the necessity of causation--that ‘something cannot be produced by nothing’--as well as Clarke’s--that ‘if anything wanted a cause it would produce itself, _i.e._ exist before it existed’--are merely different ways, as Hume shows, of assuming the point in question. ‘If everything must have a cause, it follows that upon exclusion of other causes we must accept of the object itself, or of nothing, as causes. But ’tis the very point in question, whether everything must have a cause or not’. [1] On that point, according to Locke’s own showing, there can be no certainty, intuitive or demonstrative; for between the idea of beginning to exist and the idea of cause there is clearly no agreement, mediate or immediate. They are not similar feelings, they are not quantities that can be measured against each other, and to these alone can the definition of knowledge and reasoning, which Hume retained, apply. There thus disappears that last remnant of ‘knowledge’ in regard to nature which Locke had allowed to survive--the knowledge that there is a necessary connection, though one which we cannot find out. [2] [1] P. 382. [Book I, part III., sec. III.] [2] cf. Locke IV. 3, 29, and Introduc, par. 121. Three points to be explained in the inference according to Hume. 289. Having thus shown, as he conceives, what the true answer to the first of the above questions is not, Hume proceeds to show what it is by answering the second. ‘Since it is not from knowledge or any scientific reasoning that we derive the opinion of the necessity of a cause to every new production,’ it must be from experience; [1] and every general opinion derived from experience is merely the summary of a multitude of particular ones. Accordingly when it has been explained why we infer particular causes from particular effects (and _vice versâ_), the inference from every event to a cause will have explained itself. Now ‘all our arguments concerning causes and effects consist both of an impression of the memory or senses, and of the idea of that existence which produces the object of the impression or is produced by it. Here, therefore, we have three things to explain, viz. _first_, the original impression; _secondly_, the transition to the idea of the connected cause or effect; _thirdly_, the nature and qualities of that idea.’ [2] [1] P. 383. [Book I, part III., sec. III.] [2] P. 385. [Book I, part III., sec. V.] _a_. The original impression from which the transition is made, and _b_. The transition to inferred idea