Read the quote from james madison.

if men were angels, no government would be necessary. . in framing a government which is to be administered by men over men, the great difficulty lies in this: you must first enable the government to control the governed; and in the next place, oblige it to control itself.

the main idea that madison addresses is why the us government

The main idea that Madison addresses is why the US government is needed.

James Madison starts the paragraph by presenting a hypothetical situation "if men were angels..." he tries to convey that if men were perfect, the establishment of a government in society wouldn't be needed since there wouldn't any conflicts, crime, disorganization or injustices. However, we are "imperfect" individuals, we aren't all wise enough to peacefully create and maintain a society in the benefit of all, hence the government is needed.

Furthermore, according to one of the founder father of America, we don't only need a government that governs the people but also governs itself, this latter referring that government must be balance and check by its parts (The branches of the Judicial, Legislative and Executive).

answer: president kennedy is vowing to protect freedom in this paragraph.

i belive the classic sword and a shield would do