“I do not understand anything I see in this room [on this street, from this window, in this place].”
You understand the role an object plays in your experience through the meaning you have assigned to it. When you strip an object, like a door, from the role and meaning you have assigned to it, what remains is an object of certain dimensions that consists of a certain substance. Those attributes come to you through the physical senses. You cannot observe properties that lie beyond those senses.
Likewise with people. You understand a person in your life according to the role and meaning you have assigned to that person. When you let go of the role and meaning you have assigned, what remains is a creature that is mostly unknown to you.
The aim of this exercise is to help you become aware of the labels (role and meaning) you have assigned to everything: things, people, circumstances. When you let go of those labels, you won’t end up in an abyss. The promise of the Course is that when you withdraw or suspend your personal interpretation, a new world will open up that you have yet to begin to understand.
The first series of lessons are assisting you in withdrawing, if only for a moment, the meaning you have habitually assigned to everything you see in this room, on this street, from this window, in this place.