It isn't possible to write an interpreter for this language... When the canonical form was an interpreter written by a high school kid using the manual for the language ...
Lisp 1.5 uses F-EXPR, quoteval, and the basic forms from LISP. Nothing difficult there.
But again, something that has already been done cannot be labelled as impossible.
If you provide no further proof for your somewhat outrageous claim, then your statements are no more than a tale told by an idiot, full of sound and fury. Signifying nothing.
Edit: Sarcasm has problems translating across textual barriers. Try denoting future comments as such, or to avoid downvotes, avoid them altogether on HN.
Lisp 1.5 wasn't just a theory, and ran on the PDP-1, thanks to Peter Deutsch.
Here's a copy that can run on an IBM 7094 emulator. [0]
Several people have made interpreters over the years. [1][2][3]
[0] http://www.sonoma.edu/users/l/luvisi/
[1] http://mentallandscape.com/Lisp.htm
[2] https://www.oskarth.com/lisp-interpreter/
[3] https://www.cl.cam.ac.uk/~mom22/tphols09-lisp.pdf