VERBS, AUXILIARY. May, can; original and subsequent meaningCan, May, Might. May originally meant "to be able" (E. E. "mag;" A.-S. "magan;" German "mögen"). A trace of this meaning exists in the noun "might," which still means "ability." Thus we find “I am so hungry that I may (can) not slepe.” CHAUCER, Monke's Tale, 14,744. “Now help me, lady, sith ye may and can.” Knighte's Tale, 2,314. In the last passage may means "can," and "ye can" means "ye have knowledge or skill." This, the original meaning of "can," is found, though very rarely, in Shakespeare:
i.e. "they are well skilled."
“I've seen myself and served against the French,
And they can well on horseback.
And perhaps in
“And the priest in surplice white
That defunctive music can.
“The sum of all I can, I have disclosed;
Why or for what these nobles were committed
Is all unknown to me, my gracious lady.
A trace of this emphatic use of can is found in
“The strong'st suggestion
Our worser genius can
But, as "can" (which even in A.-S. meant "I know how to" and therefore "I am able") gradually began to encroach on may, and to assume the meaning "to be able," may was compelled to migrate from "ability" to "possibility" and "lawfulness." Thus "mögen" signifies moral, "können" physical, possibility. In the following passage: “From hence it comes that this babe's bloody hand
“What can man's wisdom
In the restoring his bereaved sense?
May not be cleansed with water of this well,” F. Q. ii. 10. it is not easy at once to determine whether may means "can" or "is destined," "must," "ought." Hence we are prepared for the transition which is illustrated thus by Bacon:1
For what he may do is of two kinds, what he may do as just and what he may do as possible.