Institutio Oratoria

I in addition to quoting the authority of orators and historians maintained that I was also supported by analogy. For when I found ni ita pacunt in the Twelve Tables, I noted that cadunt provided a parallel: it was clear therefore that the present indicative, though now obsolete, was paco on the analogy of cado, and it was further obvious that we say pepigi for just the same reason that we say cecidi.

But we must remember that analogy cannot be universally applied, as it is often inconsistent with itself. It is true indeed that scholars have attempted to justify certain apparent anomalies: for example, when it is noted to what an extent lepus and lupus, which resemble each other closely in the nominative, differ in the plural and in the other cases, they reply that they are not true parallels, since lepus is epicene, while lupus is masculine, although Varro in the book in which he narrates the origins of Rome, writes lupus femina, following the precedent of Ennius and Fabius Pictor.

The same scholars, however, when asked why aper became apri in the genitive, but pater patris, asserted that aper was an absolute, pater a relative noun. Further since both words derive from the Greek, they took refuge in the fact

But how will they evade the difficulty that feminine nouns whose nominative singular ends in -us never make the genitive end in -ris, and yet the genitive of Venus is Veneris: again nouns ending in -es have various genitive terminations, but never end in -ris, but yet we have no choice but to make the genitive of Ceres Cereris?

Again what of those words which, although identical in the form of the nominative or present indicative, develop the utmost variety in their inflections. Thus from Alba we get both Albanus and Albensis, from volo both volui and volavi. Analogy itself admits that verbs whose present indicative ends in -o have a great variety of perfect formations, as for instance cado cecidi, spondeo spopondi, pingo pinxi, lego legi, pono posui, fiango fregi, laudo laudavi.