An in-depth account of how English speakers think about thinking, using perspectives from etymology, metaphor and cognitive linguistics. Cognitive linguistics addresses how we conceptually structure and linguistically categorize experience in order to render our world coherent and accessible. One of the ways we do so is through the creation of spatial metaphors. In cognitive theory, language is not regarded as a representation of objective reality, but rather, as the product of our interaction with the world as entities in three-dimensional space. The metaphors we use to structure experience conceptually are grounded in this interaction. Our ability to generate metaphors makes it possible for us to get a mental and linguistic grip on abstract concepts by representing them as tangible, concrete entities situated in space. Hence, from a cognitive perspective, metaphors are much more than occasional ornamental figures of speech occurring primarily in literary contexts; rather, they are all-pervasive components of everyday language and reflections of how we cognitively structure our world. It should come as no surprise then that, as we shall see, metaphorical expressions are particularly prevalent in the lexis of that most abstract of realms, the realm of thinking.