Why is this statement considered a theme and not a plot summary?

Success is possible through hard work and perseverance.

That's because this statement actually shows and teaches the reader something important they can take with them through life. The point of a plot summary is to explain what a plot is about, or what's happening inside. This statement doesn't seem to explain anything about a plot, or event in a story.

Explanation:

paine is arguying that they had tried everything before coming to the conclusion that they needed to fight for their freedom.

argument: "every quiet method for peace hath been ineffectual."

claim 1: "our prayers have been rejected with disdain; and only tended to convince us, that nothing flatters vanity, or confirms obstinacy in kings more than repeated petitioning and nothing hath contributed more than that very measure to make the kings of europe absolute."

claim 2: "wherefore, since nothing but blows will do, for god’s sake, let us come to a final separation, and not leave the next generation to be cutting throats, under the violated unmeaning names of parent and child."