Lack of gender agreement in Aeneid iv.169-70

Question

I was thrown by the lack of gender agreement in line iv.169 of the Aeneidː

Ille dies primus leti primusque malorum // causa fuit;

I translate: “That was the first day of death, and was the first cause of evils.” But it then seems that both instances of ‘primus’ should be feminine, as they modify respectively ‘dies’ and ‘causa’.

The only explanation I can come up with is that the masculine endings are used for the sake of the meter. In the edition I'm reading (Bolchazy), the vowel lengths are marked as: “Ille diēs prīmus lētī prīmusque malōrum.” This parses into dactyl-spondee-spondee-spondee-dactyl-spondee: (Ille di)(ēs prī)(mus lē)(tī prī)(musque ma)(lōrum). But that parsing would not work if we had ‘prīma’ instead, with its short final vowel.

It feels odd for metrical considerations to be influencing grammatical agreement. Is there something else going on here?

EDIT: I notice from the Perseus website that John Conington also regards this as something of a mistake:

We might have expected “prima,” agreeing with ‘caussa:’ but Virg. seems to have mixed up two expressions, ‘that day was the first day of ruin,’ and ‘that day was the cause of ruin.’

Answer 1

Primus (in both instances) is not modifying causa, but is a predicative adjective going with dies.

Sentences where the action is modified by words like "first" or "last" generally work differently in Latin than they do in English. In English we'd usually either use an adverb or an infinitival clause depending on a substantivized adjective:

• I did it first. (adverb)
• I was the first to do it. (substantivized adjective with infinitival clause)

In Latin, however, the ordinal generally appears as a predicative adjective agreeing with whatever it refers to:

• Primus id feci.
• hoc primus frater meus in Asia fecit "My brother was the first to do this in Asia" (Cicero, Pro Flacco 33)

Similarly in your sentence: Ille dies primus leti/malorum causa fuit can be translated as "That day first was the cause of ruin/evils" or "That day was the first to be the cause of ruin/evils", which should make it clear why "first" agrees with "day". (Of course it's perfectly valid to translate "That day was the first cause of ruin/evils", as well, but the Latin structure is less clear there.)

Answer 2

In this case primus agrees with dies and not with causa. According to John Conington, Virgil seems to have mixed up two expressions. Taken from his notes (1876):

We might have expected “prima,” agreeing with ‘causa:’ but Virg. seems to have mixed up two expressions, ‘that day was the first day of ruin,’ and ‘that day was the cause of ruin.’

A possible interpretation can be that it expresses both "first day" and "the day that was the cause of death and woe". It was the first day in the capacity of being the cause of death and woe.

The word dies can be both masculine and femine. A form can be chosen for metric reasons, e.g. (also from the Aeneid, 6.429):

[infantes] abstulit atra dies et funere mersit acerbo;

Answer 3

The word dies can be either feminine or masculine. The gender has an effect on meaning. Consult dictionaries or these questions for details:

• When is "diēs" masculine, when is it feminine, and why can this word take different genders?
• Meaning of "dies illa" from Dies Irae
• Are there nouns that change meaning based on gender?

The structure of the sentence you quote is "X was the reason", X causa fuit. Both instances of primus go into the X¹ and do not interact with the number, case, or gender of causa. Nothing within X modifies causa, except perhaps malorum — and even that is not an adjective attribute but a genitive.

To understand the structure better, strip all attributes and try to boil down the sentence to a simpler statement. Here it could be ille dies causa fuit. Start with that and expand by adding details. Identifying the core helps immensely and saves time.

Choosing endings of the wrong gender for the sake of the metre is something I have never seen. A far better working hypothesis is always that there is something about syntax, morphology, or vocabulary that you missed. My experience with classical Latin shows that in cases of confusion the mistake is always mine, not the author's — the possible liberties poets may take should be covered in a good grammar.

If you want more details on how the whole thing works out, I recommend offering your own translation of the whole quote. Discussing the details is much more fruitful if you provide a starting point, even if — no, particularly if! — you have to skip some words or are unsure about some things.

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¹ X = ille dies primus leti primusque. Whether malorum goes with causa or something else (e.g. the second primus) depends on context, but that is a minor detail.