II. Subjunctive of Purpose.
223. The subjunctive, especially be, may, might, and should, is used to express purpose, the clause being introduced by that or lest; as,—
It was necessary, he supposed, to drink strong beer, that he might be strong to labor.—Franklin.
I have been the more particular...that you may compare such unlikely beginnings with the figure I have since made there.—Id.
He [Roderick] with sudden impulse that way rode, To tell of what had passed, lest in the strife They should engage with Julian's men.—Southey.