Is John Gabriel simply schizophrenic or a really dedicated fucking shitposter? The man not only does not believe in real numbers but, he also invented his own bullshit school of Calculus that he claims is the only correct.

He wrote an entire 140-page booklet on his "New Calculus":
https://drive.google.com/file/d/1CIul68phzuOe6JZwsCuBuXUR8X-AkgEO/view

Also, for some reason, this man has some really bizarre hatred for Gilbert Strang and the rest of the Mathematical community.