Scholarly interest in credibility dates back to Aristotle’s writings on rhetoric and specifically on his notions of ethos (appeal based on the character of a speaker), pathos (appeal based on emotion), and logos (appeal based on logic or reason). More modern accounts of credibility define it as the believability of a source, and it rests largely on perceptions of the trustworthiness and expertise of the information source as interpreted by the information receiver (Hovland et al., 1953). This definition guided research on credibility in psychology and communication, which largely focuses on source credibility, typically conceptualized as the believability of a speaker and closely aligned with Aristotle’s notion of ethos.Research in the field of information science has focused instead on the credibility of information, where the emphasis has been on believability of messages rather than speakers, which is somewhat akin to Aristotle’s notion of logos. Attention to these varying conceptualizations of credibility is necessary in the digital realm, as determinations of credibility online may rest on evaluations of the source of some information, the message alone (as when source information is obscured), or on a combination of the source and the message.