Speakers appeal to logos, or reason, by offering clear, rational ideas. Appealing to logos (Greek for “embodied thought”) means thinking logically—having a clear main idea and using specific details, examples, facts, statistics, or expert testimony to support it. Creating a logical argument often involves defining the terms of the argument and identifying connections such as causality. It can also require considerable research. Evidence from expert sources and authorities, facts, and quantitative data can be very persuasive if selected carefully and presented accurately. Sometimes, writers and speakers add charts and graphs as a way to present such information, but often they weave this information into their written argument.

Although at first, Lou Gehrig’s speech may seem largely emotional, it is actually based on irrefutable logic. He starts with the thesis that he is “the luckiest man on the face of the earth” and supports it with two points: (1) the love and kindness he’s received in his seventeen years of playing baseball and (2) a list of great people who have been his friends, family, and teammates in that time.