This poem is a particularly difficult one, since its meaning is primarily syntactic, rather than conceptual.
The poem rests on the fact that, in the first line, "not" becomes a verb and then, in the second line, because of its position, it becomes a noun. Therefore, in its conceptual section, the reader's mind must realign itself before the sentences will make sense.
This realignment expresses the most general meaning of the poem, and the illustrations that follow in sections 2 and 3 are merely particularizations of this deeper level. In the physical or human realm, therefore, we have only to think of some of the dominant crusades of the past generation.
For example, I am immediately reminded of the following historical visual scheme: Dr. Martin Luther King leading a civil rights march in a Southern state. This would be underlined by the first line of the poem: "Do not.'
The second, would be a black children integrated into the same school room as white children. This would be underlined by the second line of the poem: "Let not do you."
This is only one example, of course. It could be replaced by any one of the great civil rights, or humanitarian, causes in which a small group of dedicated people did not allow the old status to stand, and modifed that unjust situation by their doing not.
When we move this same concept to the transcendental realm, we again encounter a series of manifestations throughout the history of religious symbology. Every religion, since the beginning of time, has dealt with the problem of death, and its negation. Most have symbols dealing with these two phases of the problem — either the acceptance of death, or its denial.