This distinction suggests an important remark as to the whole nature of Sensation, namely, that there can hardly be such a thing as pure Sensation, meaning Sensation without any admixture of the Intellect. We may attribute this purity to the earliest impressions made upon the mind, but not to anything known in the experience of the adult. This mixture of Intellect with Sense is not confined to Retentiveness; the other intellectual functions, Discrimination and perception of Agreement, are inseparable from the exercise of the senses. We cannot have a sensation without a feeling of difference; warmth is a transition from cold, and a conscious discrimination of the two facts. So, whenever we repeat a sensation, we have the consciousness of the repetition, or agreement. Were not these modes of consciousness present, we should have no sensation, indeed no consciousness. There is thus no hard line between sense and intellect. The question as to the origin of our Ideas in Sense is not a real question, until we explain what we mean by Sense, and make allowance for this unavoidable participation of Intellect in sensation. 4. Sensation is commonly used to employ the whole of our primary feelings and susceptibilities, as opposed to the Emotions which are secondary or derived. It thus confounds together two different sides of our susceptibility, the active and the passive; the feelings arising in connection with our exertion of inward force or energy, and those arising under impressions from external things. Both are primary states of consciousness; they are alike dependent on modifications of our sensitive tissues. But, between the two, there is a contrast, wide, deep, and fundamental, completely missed by the older Psychologists, to the detriment of their handling of such vital questions as the origin of knowledge, and the perception of a material world. The name Sensation, pointing immediately to {68} the operation of the five senses, gave the slip to the feelings of energy, or brought them in partially and inadequately. Yet it is the only name we have for the primary susceptibilities of the organism including both movement and passive sensibility.--_B._] [Editor's footnote 24: A question which, as far as I know, has been passed over by psychologists, but which ought not to be left unanswered, is this: Can we have ideas of ideas? We have sensations, and we have copies of these sensations, called ideas of them: can we also have copies of these copies, constituting a second order of ideas, two removes instead of one from sensation?