[coophitter]

I found a dictionary that defined "imperative" in certain contexts as: "absolutely necessary". The same dictionary defined "essential" in certain contexts as: "necessary". Thomas Jefferson once remarked that "the greatest of all talents is that of not using two words when one will do." Another great talent is that of not using two golf strokes when one will do. If something is "necessary" it doesn't need "absolutely" to modify it. Even dictionaries don't always succeed in demonstrating the talent that Jefferson declared to be so great. Imperative and essential are synonyms and only an author's intended or perceived semantic difference between the two could possibly convey a difference in meaning between the two.

I would treat TGM's "essentials" and "imperatives" as interchangeable or equal unless you want to give one a certain "absolute" that the other doesn't quite deserve. If you do give one more absoluteness than the other, "imperative" usually wins the debate as to which is the stronger word. A cultural difference versus a relative sameness.