phase of the god's activity. Such an adjective was called a _cognomen_,
and was often of very great importance because it began to be felt that
a god with one adjective, _i.e._ invoked for one purpose, was almost a
different god from the same god with a different adjective, _i.e._
invoked for another purpose. Thus a knowledge of these adjectives was
almost as necessary as a knowledge of the name of the god. The next step
in the development was one which followed very easily. These important
adjectives began to be thought of as having a value and an existence in
themselves, apart from the god to which they were attached. The
grammatical change which accompanied this psychological movement was the
transfer of the adjective into an abstract noun. Both adjectives and
abstract nouns express quality, but the adjective is in a condition of
dependence on a noun, while the abstract noun is independent and
self-supporting. And thus, just as in certain of the lower organisms a
group of cells breaks off and sets up an individual organism of its own,
so in old Roman religion some phase of a god's activity, expressed in an
adjective, broke off with the adjective from its original stock and set
up for itself, turning its name from the dependent adjective form into
the independent abstract noun. Thus Juppiter, worshipped as a god of
good faith in the dealings of men with one another, the god by whom
oaths were sworn under the open sky, was designated as "Juppiter,
guarding-good-faith," Juppiter Fidius. There were however many other
phases of Juppiter's work, and hence the adjective _fidius_ became very
important as the means of distinguishing this activity from all the
others. Eventually it broke off from Juppiter and formed the abstract
noun _Fides_, the goddess of good faith, where the sex of the deity as a
goddess was entirely determined by the grammatical gender of abstract
nouns as feminine.

This is all strange enough but there is one more step in the development