How is capitalization being used in Maya Angelou's "On the Pulse of Morning"?

Question

I was looking through Maya Angelou's "On the Pulse of Morning", and noticed that there's an interesting use of capitalization in the poem. (I checked multiple version to make sure that this was consistently used and not just one transcription's weirdness.)

For instance, the words "Rock", "River", and "Tree" are capitalized throughout the poem:

A Rock, A River, A Tree
Hosts to species long since departed
[...]
But today, the Rock cries out to us, clearly, forcefully
[...]
Across the wall of the world,
A River sings a beautiful song
[...]

This I interpreted as these three things being the main theme of the poem, and so worthy of capitalization. But then I came to this stanza:

So say the Asian, the Hispanic, the Jew
The African and Native American, the Sioux,
The Catholic, the Muslim, the French, the Greek
The Irish, the Rabbi, the Priest, the Sheikh,
The Gay, the Straight, the Preacher,
The privileged, the homeless, the Teacher.
They hear. They all hear
The speaking of the Tree.

Every single person here (such as Gay, Straight, Teacher) is capitalized except for "privileged" and "homeless". I found this odd; why would these two specifically be not capitalized? Sure, words like Asian, Muslim, Irish usually get capitalized... but "teacher", "preacher", "gay", "straight" etc. don't. Once you're capitalizing some of these words, why not all of them?

Why are these two words in particular not capitalized, and how does it tie in to how capitalization is used in the poem as a whole?

Answer 1

The difference is based in grammar. The capitalised terms fall into two groups. There are the straightforward nouns, 'Rock' and 'River' etc preceded by an indefinite article, 'A' and which can be taken as single examples of their class, but there are also Definite Generics where the singular noun represents the whole class or category, you can have 'A Rock' is any old rock, 'The Rabbi' is all rabbis. (it does get slightly ambiguous as to whether 'The Rock' is 'the rock we mentioned a couple of lines ago' of 'the Rock that is the prototype for all rocks'. When we get to people we are on firmer ground!)

John Lawler at Ask a Linguist May 1997 takes 'tiger as an example as he explains Definite Generics

The Definite Generic refers to the Prototype of a species, roughly the image we associate with tiger. The tiger, as a prototype, has all the properties of anything we would call a tiger, except that it doesn't exist in an individual physical sense, like all real tigers do. This is a very abstract concept, and its use signals that the speaker is theorizing.

With 'privileged' and 'homeless', a single individual belonging to the privileged category is not 'a privileged', but 'a privileged person', likewise a single individual of the homeless category is not 'a homeless', but 'a homeless person'. Therefore 'The homeless' is a collective adjective which encompasses all members of that class. Free Dictionary: Collective Adjectives

Collective adjectives are a subgroup of nominal adjectives, or adjectives that act as nouns. They are used to refer to a group of people based on a characteristic that they share.

Angelou appears to have chosen to capitalise the words which denote the essence what people and things are rather than those that merely define a more transient characteristic of where they find themselves.