154 Imagination as an Aid to Vision
Sometimes they are able to do this, but usually they are not. In that case they are asked to imagine part of the letter, usually the bottom. When they have be come able to imagine this part straight, curved, or open, as the case may be, they become able to imagine the sides and top, while still holding the period on the bot tom. But even after they have done this, they may still not be able to imagine the whole letter without losing the period. One may have to coax them along by bringing the card up a little closer, then moving it farther away; for when looking at a surface where there is anything to see, the imagination improves in propor tion as one approaches the point where the sight is best, because at that point the eyes are most relaxed. When there is nothing particular to see, the distance makes no difference, because no effort is being made to see.
To encourage patients to imagine they see the letter it seems helpful to keep saying to them over and over again:
"Of course you do not see the letter. I am not ask ing you to see it. I am just asking you to imagine that you see it perfectly black and perfectly distinct."
When patients become able to see a known letter by the aid of their imagination, they become able to apply the same method to an unknown letter; for just as soon as any part of a letter, such as an area equal to a period, can be imagined to be perfectly black, the whole letter is seen to be black, although the visual perception of this fact may not, at first, last long enough for the patient to become conscious of it.
In trying to distinguish unknown letters, the patient discovers that it is impossible to imagine perfectly un less one imagines the truth; for if a letter, or any part