From William M. Kantor's 1978 review of Peter J. Cameron's
1976 book Parallelisms of Complete Designs—

"There are three ways an area of mathematics
can be surveyed: by a vast, comprehensive treatise;
by a monograph on a small corner of the field; or by
a monograph on a cross section."

An area of mathematics—

A small corner of the field—

A cross section—

Commentary:

The area— Four.
The corner— Identity.
The cross section— Window.

The three ways— December 8  ten years ago.