Less Wrong veterans be warned: this is an exercise in going back to the basics of rationality.

Yudkowsky once wrote:

What is evidence?  It is an event entangled, by links of cause and effect, with whatever you want to know about.  If the target of your inquiry is your shoelaces, for example, then the light entering your pupils is evidence entangled with your shoelaces.  This should not be confused with the technical sense of "entanglement" used in physics - here I'm just talking about "entanglement" in the sense of two things that end up in correlated states because of the links of cause and effect between them.

And:

Here is the secret of deliberate rationality - this whole entanglement process is not magic, and you can understand it.  You can understand how you see your shoelaces.  You can think about which sort of thinking processes will create beliefs which mirror reality, and which thinking processes will not.

Much of the heuristics and biases literature is helpful, here. It tells us which sorts of thinking processes tend to create beliefs that mirror reality, and which ones don't.

Still, not everyone understands just how much we know about exactly how the brain becomes entangled with reality by chains of cause and effect. Because "Be specific" is an important rationalist skill, and because concrete physical knowledge is important for technical understanding (as opposed to merely verbal understanding), I would like to summarize¹ some of how your beliefs become entangled with reality when a photon bounces off your shoelaces into your eye.