For every fact there is an infinity of hypotheses. - Robert M. Pirsig

The Professor of Philosophy seems quite aware of what has happened. His previous little eye-flick of malice toward Phædrus has turned to a little eye-flick of fear. He seems to understand that within the present classroom situation, when the time comes, he can get exactly the same treatment he gave, and there will be no sympathy from any of the faces before him. He's thrown away his right to courtesy. There's no way to prevent retaliation now except to keep covered.

In our highly complex organic state we advanced organisms respond to our environment with an invention of many marvelous analogues. We invent earth and heavens, trees, stones and oceans, gods, music, arts, language, philosophy, engineering, civilization and science. We call these analogues reality. And they are reality. We mesmerize our children in the name of truth into knowing that they are reality. We throw anyone who does not accept these analogues into an insane asylum. But that which causes us to invent the analogues is Quality. Quality is the continuing stimulus which our environment puts upon us to create the world in which we live. All of it. Every last bit of it.

Your common sense is nothing more than the voices of thousands and thousands of these ghosts from the past.