Reading a sentence "Dum fata sinunt, vivite laeti.", I wonder why Seneca used laeti(adj.) instead of laete(adv.).
I can't find usages about this in grammar books. All Latin adjectives can be used adverbially like this?
in “Dum fata sinunt, vivite laeti" (Seneca, Hercules Furens,line 178) the adjective “laeti” in the nominative masculine plural referring to the 2nd person plural, present imperative “vivite”, is a Predicate Adjective, i.e. an adjective which is used as an appositive, differently from an Attributive Adjective that simply qualifies its noun as in e.g. “bonus imperator” (a good commander).
To sum up, “Dum fata sinunt, vivite laeti", literally meaning:” While the Fates permit, live happy”, translates into English as “While the Fates permit, live happily” with the adverb instead of the predicate adjective, simply because English and Latin are different languages with different rules.
Therefore in Latin the adjective "laeti" is not used adverbially instead of the adverb "laete",but simply as a Predicate Adjective.
In Latin, in fact, adjectives can be either Attributive or Predicate: an Attributive Adjective simply qualifies its noun without the intervention of a verb or participle, expressed or implied, as e.g. in “ verbum Graecum” ( a Greek word).
Instead, all other adjectives are called Predicate Adjectives.