2

πλ
2

with the country, no man of it would ever be of the slightest
use to you in laying out your detailed plans? To that he
must have rejoined, "I do not say that because I might wish
to stick in pins in order to trace out and study the daily changes of the situations."
To that, again, my surrejoinder should have been, "Well,
General, that precisely corresponds to the advantage of a diagram
of the course of thought. Indeed, just there is the advantage of diagrams
in general. Namely, one can make exact experiments
upon diagrams, and look out for unintended change
thereby brought about in the relations of different parts
of the diagram to one another. These operations in reasoning
take the place of the experiments upon real things that one performs in chemical
and physical research. Chemists have sometimes described