Who is the unlettered muse in poem elegy written country churchyard?

In the poem "Elegy Written in a Country Churchyard," Thomas Gray refers to the "mute inglorious Milton" as the "unlettered muse." This phrase suggests that there may be many talented and gifted individuals who, due to their lack of formal education or social opportunities, remain unrecognized and uncelebrated. Gray's use of the term "unlettered" emphasizes that this person's lack of formal education does not diminish their potential for greatness or their contributions to society.