The use of photographs throughout the text is intended to elicit an emotional response from Riis's readership. He is quite literally showing them, through the use of incontestable visual evidence, "how the other half lives." This proves a convincing means of persuasion through emotional appeal, or pathos.
While the phrase has become cliché, it is undoubtedly true for Riis that, in creating How the Other Half Lives, a picture is indeed worth a thousand words. More so often than written language, an image can provoke the viewer to respond emotionally to the suffering of others. And this, in turn, might push them toward taking some sort of action. This is of particular importance given that much of Riis's domestic readership, not to mention his international readership, would likely have never seen the tenements in New York City before picking up How the Other Half Lives.
The use of photography also plays a critical role in establishing Riis as a credible journalist, contributing to the ethos of his text. Words can be used to cleverly embellish a situation, but pictures cement Riis's words as true, or, at the very least, help him emphasize the severity of the problem. As a social reformer, Riis did not want to settle for simply describing the problem, he wanted to fix it. The pictures are a necessary element of his argument, establishing credibility and provoking an emotional response to spur people into action.
Riis appeals to a wide variety of different experts throughout the text, not relying simply on his own personal account of the tenements to win readers over to his cause. This appeal to expert opinion is a form of ethos, bolstering his credibility in the eyes of his readers.
Riis begins to establish his credibility at the very outset: in the Preface, he credits three men, well established at the time as experts in their fields, as being instrumental to the creation of How the Other Half Lives. These men are Charles G. Wilson, the president of the New York City Board of Health; Chief Inspector Byrnes of the Police Force; and Dr. Roger S. Tracy, the Registrar for Vital Statistics. Riis goes on to reference Dr. Tracy's work extensively when discussing death rates in the tenements. The inclusion of these three names sets up Riis as a credible source of information: he has clearly done his research, relying on those with more knowledge when necessary. Riis's position as a well-known muckraking journalist would have made it all the more necessary that he establish this credibility. Muckrakers during the progressive era were known for writing articles that were oftentimes salacious or sensationalized; Riis, therefore, must establish this ethos in his writing in order for the tenement issues to be taken seriously by the public.
