One of the book’s themes concerns the ways in which the fallibility of the mind leads us to essentially fool ourselves, resulting in the possibility of error. The text explores the mind’s many ways of doing, such as perceptual phenomena that trick us and psychological tendencies that ensure we are bad at knowing we do not know.

A prominent thread in the book is the idea that our senses can fail us, no matter how convincing they seem. Perception, says the author, is the interpretation of sensation, which leaves room for our minds to diverge from the world, allowing error to creep in. The author cites John Ross’s mirage at Lancaster Sound as an example of perceptions being quite convincing but still wrong. Since we cannot consciously perceive the brain’s corrective processes, we feel our perception is infallible.

However, the author, making the case that the mind does not reflect reality, highlights the gap between us and the world. Schulz uses the example of coherencing, in which the brain corrects our viewing experience despite the blind spot of the eye, where the optic nerve goes through the retina. This perceptual trick produces a seamless visual experience, even though this perception does not reflect reality.