The fact is, to repeat, that _any idea is made into an abstract idea when context and determination carry the meaning of abstractness_; and there is no doubt that, in minds of a certain type, imaginal processes other than words may take on this context and suffer this determination, so that _thought may go on in imaginal terms_. Experiments show that visual imagery may play its part, along with verbal ideas and attitudes, in a single train of thought; one recent writer describes visual images of a complex kind as centres of ‘activity’ in the progress of thinking. Blindfold chess-players, if they are of the motor type, think of attack and defence in terms of ‘lines of force’ which connect the various pieces on the board, and which they themselves ‘feel’ in kinæsthetic imagery as pushes and pulls in hand and arm. We saw on p. 77 that such general notions as ‘virtue’ and ‘commerce’ may come to mind in the form of habitual images. No doubt, these images were at first contextual processes surrounding a verbal idea; they are therefore secondary, and not original; yet they may now replace the verbal idea, and do duty by themselves as abstract ideas. There are probably a good many of us whose abstract idea of ‘triangle’ is simply a mental picture of the little equilateral triangle that stands for the word in text-books of geometry. _Is there, then, no truth at all in the theory of the composite photograph?_ Not an atom, so far as regards the genesis of the abstract idea; one might superpose individual ideas _ad infinitum_, and one would still have nothing more than an individual idea. But if we leave the abstract idea out of the question, and consider the _history of ideas_, in minds of the imaginal type, then the composite photograph has more to say for itself. For we know from p. 156 that the associative tendencies, if left to themselves, gradually die out; and that the weaker die out more quickly than the stronger. Consider what this means! I have a mental picture of a landscape, and I do not see the actual scene for some years. The picture fades out; but it fades out unevenly; its various features are correlated with associative tendencies of varying strength. So I shall always imagine a semicircle of mountains with the valley opening towards me, and the river meandering down the valley; for these are features common to many landscapes and strongly impressed upon my nervous system; but I shall lose the relative heights of the mountains, and the particular turns of the river, and the special distribution of villages and churches; for these are individual features, and have been less frequently repeated. _My mental picture of the landscape thus approaches a type_; and the same thing is true of all complex images, if they are left to themselves, and the underlying associative tendencies decay from old age. These typical images are, nevertheless, ideas of particular scenes or things or faces; their rounding and smoothing do not make