Dative of Purpose & Double Dative
The dative of purpose names what something is FOR — auxiliō "for help," subsidiō "for support," impedīmentō "for a hindrance." Caesar leans on it constantly: tertiam aciem laborantibus nostrīs subsidiō mīsit — "he sent the third line as support for our struggling men."
Notice that sentence has TWO datives — subsidiō (the purpose) and nostrīs (the people it serves).
That is the famous double dative: a dative of purpose paired with a dative of reference, both depending on the same verb (almost always sum or a verb of motion). The pattern is so fixed that Latin idioms like cui bonō? ("to whose benefit?"), cordī est ("it is dear to"), and hoc tibi dōnō est ("this is a gift for you") are all double datives waiting to be recognized.
Learnings0 core · 1 AP claim
AP framework claims (1)— verbatim from AP CED
"X serves as [purpose] for [person]" — almost always with sum (est, erat, fuit) or a giving/sending verb
The purpose dative is regularly an ABSTRACT noun, SINGULAR, unmodified except by māgnō, summō, minōrī, etc.
See It In Action
— B. G. i. 52. 7
Textbook double dative. Subsidiō is what the line serves AS; nostrīs names whom it serves. Two datives, one verb.
— B. G. i. 25. 3
Notice māgnō — adjectives of degree are the ONE thing allowed to modify a purpose dative. Māgnō impedīmentō, summō ūsuī, minōrī cūrae — same shape every time.
— B. G. iv. 25. 1
Māgnō ūsuī fuit is Caesar's stock formula for "X paid off." Once you've seen it, you'll see it ten times a book.
— Liv. i. 39
Cordī est is a frozen idiom: "is heart-dear to." Don't translate cordī as "of the heart" — translate the whole phrase as one English verb: "is dear to," "pleases."
Latin has multiple ways to say "for the purpose of." The dative version is narrow — it only works for a fixed list of abstract nouns.
what something serves AS — frozen list
auxiliō vēnit
he came as / for help
general-purpose purpose — works anywhere
ad auxilium ferendum vēnit / ut auxilium ferret
he came in order to bring help
Tip: Ask: is the noun on the short list (auxiliō, ūsuī, subsidiō, salūtī, cordī, cūrae, dōnō, exemplō, impedīmentō)? If yes, dative. Otherwise reach for ad + gerund(ive) or ut + subjunctive.
In Caesar's tertiam aciem laborantibus nostrīs subsidiō mīsit, what role do nostrīs and subsidiō play?
Study Tips
- •When you see two datives stacked on the same verb, ask: which one names the THING-FOR-WHICH (purpose), and which names the PERSON-FOR-WHOM (reference)? That's the double dative.
- •The purpose dative is almost always abstract and singular — auxiliō, ūsuī, salūtī, cordī, cūrae. Memorize the short list; it covers most occurrences.
- •Translate X est Y dat. Z dat. as "X serves as Y for Z" or "X is a Y to Z," then polish the English. Literal first, smooth second.
- •Watch for the verb sum hiding the construction — cordī erat doesn't mean "was of the heart," it means "was dear to."