past of Memory (sometimes perhaps also the present of Attention) and combines it with a conjectured future in such a way as to produce a whole. It is always seeking for likenesses, orderly connections, regular sequences, beautiful relations, suggestions of unity in some shape or other, so as to reduce many things into one and to obtain a satisfying picture.
For example, suppose a large mill-wheel at rest to be almost hidden from my eyes by intervening trees so that, even if it were moving, I could only see one spoke at a time; and at present I am not aware that it is close before me. Something begins to move. I look up. Attention tells me that I see before me, moving from left to right, something like a plank or pole: it passes and I see nothing; but then comes another similar object moving similarly; then a third, rather quicker; then a fourth, quicker still. The mind at once sets to work to find the cause. The Memory tells me that I have seen simply a number of poles or planks moving from left to right with quickened motion; the Attention tells me that I see one now; but the Imagination, taking in the isolated reports of Memory and Attention, includes them in a larger hypothesis of her own, in which, if I may so express it, the constituent elements, the spokes, are subordinated, and the explanatory unity, the wheel, is brought into prominence: and thus the motion from left to right, which explained nothing, is replaced, in my mind, by the motion of revolution, which explains everything.
It is on the basis of the Imagination, aided by Experience and Reason, that we establish our conviction of the permanence of the simplest Laws of Nature. This I have touched on in one of my previous letters. The Memory, recalling the sight of many stones falling to the ground, comes perhaps to the aid of Attention, as a child notes a particular stone falling to the ground, and
