462 A. BAIN : under the retentive or adhesive attribute of our nature, with which we are so marvellously gifted ; and any other process of development is quite secondary in comparison. If we add the great extension of our resources by similarity, or transferring old adhesions to new connexions, I think there is comparatively little left to correspond to a process of differentiation. There is indeed something, and that some- thing is also of importance, namely, improvement in our powers of discrimination. Even our primary sensibility to differences of colour, or tone, can be cultivated, as is gene- rally believed ; and we may, if we please, call this " differen- tiation of a continuum ". To take Mr. Ward's example, the steel-worker sees half-a-dozen tints, where others see only a uniform glow. It is to my mind sufficient to describe this as the education or cultivation of a difference. I see nothing gained by stating it otherwise. Every new shade of diffe- rence is a new presentation. If I were to use the word "differentiating" I would not couple it with a continuum, but with a uniform effect : continuity, in the meaning of sequence, has no relevance. With many of Mr. Ward's statements as to the facts of our presentations I thoroughly agree. I perfectly admit that what we usually call a sensation of one of the senses does not typify an elementary presentation. I also admit what he says as to one circumstance in the effect of repeti- tion upon our sensations, namely, when they are complex, as from a flower, to make us more and more cognisant of the details. But when the sensation is simple, as the colour of gold, or when the details of a complex sensation have been mastered, repetition has the effect of deepening the impres- sion on the memory and nothing else. An interesting discussion follows on " latent mental modi- fications," which the author transforms into a doctrine of " sub-consciousness," all which I think happy. Our con- sciousness at any moment can be distinguished into a centre or focus of attention, and a wider field, over which attention may range so as to shift the focus from one moment to another. Outside this field are presentations just out of consciousness, and ready to be brought in by the slightest accessions of relative intensity which may come over them, even though they are not in the field. These are " sub-conscious" states, and the designation is a useful addition to our nomenclature. We have never, I think,' taken sufficient notice of the multi- tude of recent impressions, that are a power in our minds, from their readiness to appear in consciousness again and again, and which serve as guides to immediate action in our
