Metaphor is a figure of speech that describes one thing in terms of another, ignoring literal differences in favor of some similarity the author wants readers to notice. Most people come away from their English or literature courses with the impression that this is all metaphor is, a poetic device that might be pretty but is always unnecessary and may even obscure the real world or obstruct technical discussions.

This isn't how linguists and cognitive scientists think of metaphor, however. Decades of research into the nature of metaphor suggests that conceptual metaphors are pervasive, and much of our reasoning power and ability to build and understand abstractions is based on metaphor. Some of these conceptual metaphors, such as understanding and talking about time, by relating it to properties of physical space, are "dead" to us; that is, we no longer feel that they are metaphors, but it's difficult to think of "time" without those metaphors. Some, such as "time is money", are more obviously metaphorical but influence our unconscious understanding of time and what we think about it.

We'll examine the necessity of conceptual metaphors and what makes metaphors good or bad, in what they conceal or reveal about things and their relationships. We'll look at the ways mathematics relies on metaphor, and the metaphorical nature of how we think about computers, programs, interfaces -- and, yes, monads. Finally, with an eye toward better pedagogy and building better interfaces, we'll see how finding new metaphors can help us see new truths about the world by revealing facets of abstractions that other metaphors have concealed.