Why is it important to determine the central idea of a speech or essay?

It is important to determine the cental idea of a speech or essay so that you can better understand the entire speech/essay. Then in the end when you understand the entire speech/essay you can use it to help you through life and maybe learn something from it.

It is important to identify the central idea of a speech or an essay as it helps the listener/reader understand the meaning and objective of the entire piece. Otherwise, losing oneself in the meaningless gibberish of the speaker/author is very likely, as for one is hard to find interest in something that virtually is going nowhere.

Once the central idea is identified, it is easy to go along the main topic and subtopics, as well as formulating one's own conclusions at the end.

1. read the following excerpt from franklin d. roosevelt's "fireside chat 19":

on the other side of the picture, we must learn also to know that guerilla warfare against the germans in, let us say serbia or norway, us; that a successful russian offensive against the germans us; and that british successes on land or sea in any part of the world strengthen our hands.

remember always that germany and italy, regardless of any formal declaration of war, consider themselves at war with the united states at this moment just as much as they consider themselves at war with britain or russia. and germany puts all the other republics of the americas into the same category of enemies. the people of our sister republics of this hemisphere can be honored by that fact.  

the true goal we seek is far above and beyond the ugly field of battle. when we resort to force, as now we must, we are determined that this force shall be directed toward ultimate good as well as against immediate evil. we americans are not destroyers — we are builders.

analyze the effectiveness of this excerpt. how does it function within the speech as a whole? how does the structure of the excerpt to convey the speech's purpose and key points? support your argument with evidence from the speech. (10 points)

the eye wink at the hand; yet let that be / which the eye fears, when it is done, to see.