Both Uses of

derive

in

Crediting Poetry by Seamus Heaney

…heritages; but surely every dweller in the country must hope that the governments involved in its governance can devise institutions which will allow that partition to become a bit more like the net on a tennis court, a demarcation allowing for agile give-and-take, for encounter and contending, prefiguring a future where the vitality that flowed in the beginning from those bracing words "enemy" and "allies" might finally derive from a less binary and altogether less binding vocabulary.†

It is an adequacy deriving from what Mandelstam called "the steadfastness of speech articulation," from the resolution and independence which the entirely realized poem sponsors.†
*

Definition:

(derive)
to get something from something else

(If the context doesn't otherwise indicate where something came from, it is generally from reasoning--especially deductive reasoning.)