Anton’s Syndrome is a disorder that belongs to a group of neurological problems known as anosognosia—the denial of disease. Anton’s Syndrome specifically refers to a condition in which blind people do not know they are blind. The author uses this condition to demonstrate that error knows no limits and that any form of knowledge—despite its centrality or unassailability—can fail us.

The “bias blind spot” is the psychological term for a specific asymmetry in human reasoning: If we want to discredit a belief, we will argue that others hold that belief only because it benefits them, whereas if we wish to champion a belief, we will argue for its veracity. This helps explain the reason we dismiss the self-serving facets of our own beliefs while being quick to detect them in others’.

Coherencing is the process by which the brain automatically corrects our vision despite our blind spot—the part of the eye where the optic nerve goes through the retina. Coherencing thus creates a kind of visual illusion. The author uses coherencing as an example of the unconscious perceptual processes that mask the fallibility of our perception.