Scientific explanations are central to scientific understanding. Their generation and evaluation play correspondingly central roles in scientific practice and education. The motivating idea behind the proposed research is that there is value to having more than one explanation. Explanations for the same phenomenon that take different forms or come from different domains. Having multiple explanations can promote deeper understanding and can in turn promote better learning. For example, suppose a child first learns an algebraic proof for the Pythagorean theorem. They might nonetheless come to understand it better when they learn a second, geometric proof. Or suppose you want to understand why humans use certain mental shortcuts in reasoning. One explanation might offer the cognitive mechanism or process that implements the mental shortcut; another explanation might specify its cognitive function or purpose. Having both explanations supports deeper understanding. These ideas are intuitive, but they lead to some important and unexplored questions. For example, do two explanations support deeper understanding when they are more similar to each other, or more different from each other (or something in between)? Does having access to multiple explanations sometimes support illusions of understanding? And how does the similarity or difference between explanations shape the process of inquiry – such as the questions someone asks and what they ultimately learn? This research will addre