61. This becomes clearer upon a view of the confirmations of the testimony, as Locke gives them. They all, we may remark by the way, presuppose a distinction between the simple idea as originally represented and the same as recalled or revived. This distinction, fixed by the verbal one between ‘impression’ and ‘idea,’ we shall find constantly maintained and all-important in Hume’s system; but in Locke, though upon it (as we shall see) rests his distinction between real and nominal essence and his confinement of general knowledge to the latter, it seems only to turn up as an afterthought. In the account of the reality and adequacy of ideas it does not appear at all. There the distinction is merely between the simple idea, as such, and the complex, as such, without any further discrimination of the simple idea as originally produced from the same as recalled. So, too, in the opening account of the reception of simple ideas (Book II. chap. xii. sec. 1), ‘Perception,’ ‘Retention,’ and ‘Discerning’ are all reckoned together as alike forms of the _passivity_ of the mind, in contrast with its activity in combination and abstraction, though retention and discerning have been previously described in terms which imply activity. In the ‘confirmations’ before us, however, the distinction between the originally produced and the revived is essential. They depend on language which presupposes the ascription of sensation to an outward cause. 62. The first turns upon the impossibility of producing an idea _de novo_ without the action of sensitive organs; the two next upon the difference between the idea as produced through these organs and the like idea as revived at the will of the individual. It is hence inferred that the idea as originally produced is the work of a thing, which must exist _in rerum naturâ_, and by way of a fourth ‘confirmation’ the man who doubts this in the case of one sensation is invited to try it in another. If, on seeing a fire, he thinks it ‘bare fancy,’ _i.e._ doubts whether his idea is caused by a thing, let him put his hand into it. This last ‘confirmation’ need not be further noticed here, since the operation of a producing thing is as certain or as doubtful for one sensation as for another. [1] Two certainties are not more sure than one, nor can two doubts make a certainty. The other ‘confirmations’ alike lie in the words ‘product’ and ‘organ.’ A man has a certain ‘idea:’ afterwards he has another like it, but differing in liveliness and in the accompanying pleasure or pain. If he already has, or if the ideas severally bring with them, the idea of a producing outward thing to which parts of his body are organs, on the one hand, and of a self ‘having power’ on the other, then the liveliness, and the accompanying pleasure or pain, may become indications of the action of the thing, as their absence may be so of the action of the man’s self; but not otherwise. Locke