Did grammarians consider the adverbial -e a case ending?

Question

For adjectives of the first and second declension, the corresponding adverb is formed with the ending -e. For example, pulchre (beautifully) comes from pulcher (beautiful). Canonically this -e is viewed as a suffixed used to derive adverbs from adjectives. It is also possible to view it as a case ending, and the adverb as yet another case. The line between declension and deriving adverbs is not always clear¹, since many cases of a noun make the word into an adverb of some kind.

Did any ancient or later grammarian hold or consider this view of -e (or the corresponding third declension version -iter) as a case ending? Who was the first to think or propose this? I assume this was never a popular way to see things, but it is not an entirely unreasonable idea to have. I would like to know when this idea came about.

I should add that I have never seen anyone discuss -e or -iter as case endings, but I highly doubt my idea is original.

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¹ I don't mean only Latin, but all languages that have cases. It could be that such an idea of -e as a case ending was introduced to Latin grammar by analogy to some other language. I also recognize that there are problems in viewing -e as a case ending; see comments below.

Answer 1

In a recent paper (included in The Latin of the Grammarians), I have made the point that Latin grammarians, unlike their Greek predecessors, did not expressly stress the uninflectional nature of adverbs, and this may be due to the fact that they observed some sort of declension in some types of adverbs (not only those derived of adjectives -doctus > docte-, but also the locatives, which some grammarians considered as nomina adverbialia or simply adverbia). Varro even included the type docte among the verba declinata.

More precisely, my point is that, whereas Greek grammarians used the word "ákliton" (uninflected) in their definitions of the adverb, the corresponding Latin word (indeclinabile) seems to be deliberately avoided by Roman grammarians. A revealing passage can be cited from Iulius Romanus (3rd century AD), as cited in Charisius (page 246 in Barwick's editions, and page 190 in Keil's Grammatici Latini): in that passage both the Greek and the Latin definitions are given, but only the former refers to the adverb's uninflectional nature. As for Varro, he includes the type docte among the declinata verba in De lingua Latina, book X, paragraph 17. Also, some modern scholars have dealt with adverbs as a kind of nominal cases: e. g., Calboli (1969, p. 405).

CALBOLI 1969 = G. CALBOLI¸ Review of CUPAIOLO 1967, «Lingua e stile» 2, 1969, pp. 404-406

Answer 2

As far as I can see, the Roman grammarians did not consider the adverbial -e to be a case ending. On the other hand, from the standpoint of historical linguistics most Latin adverbs are indeed fossilised case forms of adjectives. The “adverbial -e” is in fact of two-fold origin. i-stem adjectives like facilis use the accusative singular neuter as an adverb (in this instance: facile). The first/second declension adjectives form adverbs in -ē (Old Latin -ēd), the older form of the suffix for the ablative singular.

The formation of adverbs is discussed in detail in Buck’s “Comparative grammar of Greek and Latin” (1933) pp. 348-352, but in Sihler’s reworking of that book (“New comparative grammar of Greek and Latin” 1995) this section was for some reason omitted.