One of the most important contributions of Aristotle's approach was that he identified rhetoric as one of the three key elements—along with logic and dialectic—of philosophy. Indeed, the first line of the "Rhetoric" is "Rhetoric is a counterpart ("antistrophe") of dialectic". According to Aristotle, logic is concerned with reasoning to reach scientific certainty while dialectic and rhetoric are concerned with probability and, thus, are the branches of philosophy that are best suited to human affairs. Dialectic is a tool for philosophical debate; it is a means for skilled audiences to test probable knowledge in order to learn. Conversely, rhetoric is a tool for practical debate; it is a means for persuading a general audience using probable knowledge to resolve practical issues. Dialectic and rhetoric create a partnership for a system of persuasion based on knowledge instead of upon manipulation and omission.