We often take it for granted that we have some knowledge about the way reality is. For instance, it seems clear to me that I know there is a computer screen directly in front of my face, and I believe it is clearly true that I know how to get to the refrigerator from where I currently sit. But what is the nature of the computer screen and the refrigerator? Common sense tells us that they are bundles of physical stuff and that our minds have become adapted, perhaps through a process like evolution, to knowing about and acting with respect to them.