This book presents an original discussion and analysis of epistemic peer disagreement. It reviews a wide range of cases from the literature, and extends the definition of epistemic peerhood with respect to the current one, to account for the actual variability found in real-world examples. The book offers a number of arguments supporting the variability in the nature and in the range of disagreements, and outlines the main benefits of disagreement among peers i.e. what the author calls the benefits to inquiry argument.