thence certainly infer the existence of anything without us which corresponds to that idea, is that whereof some men think there may be a question made; because men may have such ideas in their minds, when no such thing exists, no such object affects their senses.’ (Book IV. chap. ii. sec. 14.) It assumes that simple ideas are consciously referred to things that cause them. 55. It is clear that here in his very statement of the question Locke begs the answer. If the intuitive certainty is that ‘the idea we _receive from an external object_ is in our minds,’ [1] how is it possible to doubt whether such an object exists and affects our senses? This impossibility of speaking of the simple idea, except as received from an object, may account for Locke’s apparent inconsistency in finding the assurance of the reality of knowledge (under the phrase ‘evidence of the senses’) just in that ‘perception’ which reaches not to intuitive or demonstrative certainty, and only ‘passes under the name of knowledge.’ In the passage just quoted he shows that he is cognizant of the distinction between the simple idea and the perception of an existence corresponding to it, and in consequence distinguishes this perception from proper intuition, but in the very statement of the distinction it eludes him. The simple idea, as he speaks of it, becomes itself, as consciously ‘received from an external object,’ the perception of existence; just as we have previously seen it become the judgment of identity or perception of the ‘agreement of an idea with itself,’ which is his first kind of knowledge. [1] I do not now raise the question, What are here the ideas, which must be immediately perceived to agree or disagree in order to make it a case of ‘intuitive certainty’ or knowledge according to Locke’s definition. See below, paragraphs 59, 101, and 147. Lively ideas real, because they must be effects of things.