The previous chapter's conclusion that minds are brains has major implications for two central philosophical questions: what is reality, and how do we know it? These questions are interrelated, as consideration of what things exist needs to fit with discussion of what it takes to gain knowledge about those things. For example, an empiricist who believes that knowledge can come only through the senses might conclude that physical objects such as lions and mountains are not real, because we sense only features of them, not the things themselves. At the other extreme, an idealist who believes that reality is inherently mental might also conclude that lions and mountains cannot be said to be real apart from how we think about them.