The Dalai Lama told me to embrace my enemies, to be thankful for them, because only my enemies could bring me challenge, and without challenge, I would never achieve Enlightenment. So I welcomed into my life all manner of obnoxious persons who disagree with me from my porkpie down to my saddle shoes. I feel much better now and have only one stop left on the road to Enlightenment.
The Dalai Lama told me that at the last stop, I would encounter my Pure Self. Asked I, “How shall I know I have arrived?” “Look to the sky,” said he, “for a cloud shaped like Lady Gaga in a dress.” “But which dress?” asked I. Said he, “The one with all the pork chops.” Think about it. It explains everything, how Life is all about living in the layers, the nuance, the many delicate balances of meaning. Or as the Dalai Lama put it, “One man’s wiener is another man’s wienerschnitzel.” (Surprised me, too. I didn’t even know he spoke German.)
At this level of Enlightenment, like you, I transcend to the modal verbs, which help me express the layers, that nuance, those delicate balances of meaning: may, might, can, could, will, would, shall, should, must, ought to. I marvel at how they attach themselves to the main verbs to coax them toward obligation, or necessity, or uncertainty, or possibility, or likelihood, or ability, or permission, or all sorts of contingencies: I go, I should go, I must go. Different modals, different meanings. Yes, Nirvana.
For those of you who have not begun the journey, the Unenlightened, I offer The Meta of Modality: first, modal verbs do not have tenses; second, they do not need to agree in number; and third, they do not conjugate. They just are. The Dalai Lama stands in a corner alone, clapping with one hand.
With so many modals shading the meaning of our sentences, we should understand their role and that we sometimes misuse them; and we should draw distinct lines where the meaning of one modal overlaps the meaning of another: like may, might, can.
I can go. (I have the ability to go.)
I may go. (I have permission to go.)
I might go. (There is a possibility I will go.)
Assign each that meaning, and use it rigidly. When we drift across the line where can also means “permission” and may also expresses “possibility,” we confuse our readers. Which is it? Here’s another trio of modals with which lawyers have wrestled for centuries: shall, will, must. Use each only for a single, narrow meaning:
He shall pay. (A weak word many experts propose we toss. I agree.)
He will pay. (His payment lies in the future.)
He must pay. (The contract obligates him to pay. That's the one we want.)
Could works well as the “past” of can, but should has little connection to shall; it leans more to the certain side of might. That leaves would and ought to, would being the gateway to a much longer discussion about the subjunctive, but I will spare you; it would only disturb the tranquility of the Now. And ought to? Think of ought to as useless, the Appendix of Modality.