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does not stand in that relation, while there is nothing to which the
second stands in that relation without the first standing in
the same relation to it; or else it is just the other way, namely
that the second stands in the relation, R, to which the first does not
stand in that relation, while there is nothing to which the first
stands in that relation, R, without the second also standing
in the same relation to it. The proof of this, which is a little
too intricate to be followed in an oral statement (although
in another lecture I shall substantially prove it) depends upon
the fact that a relation is in itself a mere logical possibility.

I will now pass to another quite indispensable
department of the gamma graphs.
Namely, it is necessary that we should be
able to reason in graphs about graphs.