In this case I think we should say that “c a d a” is the rule for drawing the design. Roughly speaking, it characterizes what we call a rule to be applied repeatedly, in an indefinite number of instances. Cf., e.g., the following case with 34):
35).   A game played with pieces of various shapes on a chess board. The way each piece is allowed to move is laid down by a rule. Thus the rule for a particular piece is “ac”, for another piece “acaa”, & so on. The first piece then can make a move like this:





, the second, like this:















. Both a formula like “ac” or a diagram like that corresponding to such a formula might here be called a rule.
36).   Suppose that after playing the game 33[(|)] several times as described above, it was played with this variation: that B no longer looked at the table, but reading A's order the letters call up the images of the arrows (by association), & B acts ◇◇◇ according to these imagined arrows.
37).   After playing it like this for several times, B moves about according to the written order as he would have done had he looked up or imagined the arrows, but actually without any such picture intervening. Imagine even this variation:
38).   B in being trained to follow a written order, is shewn the table of 33) once, upon which he obeys A's orders without further intervention of the table in the same way in which B in
31.
33) does with the help of the table on each occasion.