"Floppy disks are like Jesus. They died to become the icon of saving."— David Peter (@davidnoob) April 9, 2013
The unexpected appearance of an interpreter tended to freeze the form of the language, and some of the decisions made rather lightheartedly for the "Recursive functions …" paper later proved unfortunate. These included the COND notation for conditional expressions which leads to an unnecessary depth of parentheses, and the use of the number zero to denote the empty list NIL and the truth value false. Besides encouraging pornographic programming, giving a special interpretation to the address 0 has caused difficulties in all subsequent implementations.
— John McCarthy, History of Lisp.