Aristotle simply means that, when preparing a speech, it's important to bear in mind your target audience, the people who are actually going to hear you speak. This is a very important consideration to take into account if the speaker is going to get his message across effectively. Like most ancient thinkers, Aristotle was a firm believer in the importance of rhetoric, or the art of persuasion. And the primary purpose of making a speech is to persuade your audience of the point that you're making. Hence the necessity of the speaker's focusing his attention on the potential reaction of his audience when writing and preparing a speech.

These days, rhetoric tends to be associated in the popular mind with empty words and shameless manipulation, the province of insincere politicians who will say anything to get elected. Yet Aristotle's rhetorical model of communication still has something to say to us in this more skeptical age of ours. So long as someone has something to sell, whether it's a policy platform or a new brand of detergent, they will need to persuade other people of its benefits. And this is where focusing attention on audience reaction comes in. No amount of fine speeches or fancy words will make the slightest bit of difference to whatever it is that's being communicated unless the potential audience and its needs are taken into consideration by the speaker.