Because their teachers shared the same delusion.

Ah! Reality as a shared delusion. A variation of the "brain in a vat" conundrum.

Fair enough.

Does a shared delusion represent a valid reference?

Does that mean you are all just voices in my head? Or am I just a voice in all of your heads? Kind of a scary thought....me being inside your heads.............. :devil:

The real question is, which one of us is sufficiently insane to have created this subjective reality?

My suspicions rest with that PF character.

Did I remember to say "Bonjour Jacques"?

His insanity is in only your mind.

As each of us can be certain only that their own “I” exists, you may be correct. It is possible that “reality”, including the external world and other people have no independent existence, and are only internal events and representations.

I wonder what Dr. Freud would have to say about me somehow hallucinating all these people.

There are some days it's just not worth chewing through the straps.

The tribulations if maintaining a high fibre diet.

LOL etc.