" English has a single verb "to be," which occurs in a variety of contexts. The Guyanese have three verbs for the same set of functions. Or rather two verbs plus what we linguists call a "zero form," a verb that is "not phonologically realized" and looks to the layman like nothing at all:

I am hungry = me hongry.
The boy is laze = di bai lazy.

This is typically what happens when the predicate is an adjective. If it's a noun, you get yet another a:

I am captain = me a kyapn.

However, if the predicate is an expression indicating location, de must be used:

I am in Georgetown = me de a Jarjtong.

If there is no predicate (as in Descartes' "I think, therefore I am") then the meaning must be the same as "exist," and again de is used:

God is/exists - Gad de. "

― Derek Bickerton , Bastard Tongues: A Trailblazing Linguist Finds Clues to Our Common Humanity in the World's Lowliest Languages