  In this paper, we provide an interpretation of Book II of the Elements from
the perspective of figures which are represented and not represented on the
diagrams. We show that Euclid's reliance on figures not represented on the
diagram is a proof technique which enables to turn his diagrams II.11--14 into
ideograms of a kind. We also discuss interpretations of Book II developed by J.
Baldwin and A. Mueller, L. Corry, D. Fowler, R. Hartshorne, I. Mueller, K.
Saito, and the so-called geometric algebraic interpretation in B. van der
Waerden's version.
