Logic is the process of reasoning from a known or given to a concluding truth; it is closely aligned with rhetoric, in that an argument usually is designed to convince or to sway by means of “linguistic” (or, in some cases, visual) presentation.  If the listener to a rhetorical statement has already committed to following logic, then the speaker (agent) need only to follow the logical steps from agreed facts to proposed conclusion to convince the listener, the goal of all rhetoric.  By studying the rules of logical argument (cause/effect, inclusivity, progression, etc.), and implementing them, while avoiding the fallacies of logic (post hoc, slippery slope, argument from analogy, etc.), the speaker or writer can successfully convince the listener and win him/her over to his/her side of the rhetorical point of view.  For example, if a political figure can show the logical steps from augmenting the police patrol budget to fewer crimes on the street, the paying public will have to agree to a tax hike.