What is the purpose of dividing a persuasive argument paper into an introduction, body, and conclusion?

The purpose of dividing an argument in sections is because;

Purpose of intro:
To inform readers the topic you are trying to persuade them on.

Body: To back up your argument with evidence from multiple sources to try to get readers to be on your side.

Conclusion: To basically summarize what you just wrote and to end off your essay.

Hope that helped :)

-Smartcookies