That is true, but to engage in a bit of semiotics: those cores are hardly the most appealing part of Lisp for most of the uses cases it's found. It certainly was one way to enable the interactivity and homoiconicty and metacircularity, but, as Clojure and Janet demonstrate, there are a lot of other aspects of Lisp that have value. And while one could (and some have, IIRC) built a Lisp on those minimal data structures that doesn't have parens, most people associate Lips with them being in the strange place.

Cons/car/cdr are far less important, IMO, than eval.

Read, on the other hand, is also technically missing from Janet, and I personally don't mind a great deal, but I could see that being argued.

That specific formalism is only specific to McCarthy's implementation though, not even CL counts, as it greatly expands and derives beyond it.

Even McCarthy's lisp had iterations of itself.

Personally, I think the second paper actually points to the essential component for me:

> LISP data are symbolic expressions that can be either atoms or lists. Atoms are strings of letters and digits and other characters not otherwise used in LISP. A list consists of a left parenthesis followed by zero or more atoms or lists separated by spaces and ending with a right parenthesis. The LISP programming language is defined by rules whereby certain LISP expressions have other LISP expressions as values.

I would use that to generalize to a family of languages like so:

""" A Lisp language consists of:

1) Some data representation which are symbolic expressions that can be either atoms or lists. Atoms are strings of letters and digits and other characters not otherwise used in the given Lisp language. A list consists of a starting character (commonly left parentheses) followed by zero or more atoms or lists separated by seperator characters (commonly spaces) and ending with a terminating character (commonly right parenthesis).

2) A programming language whose code uses that data representation and is defined by rules whereby certain Lisp expressions have other Lisp expressions as values. """

Personally I think that's the key aspect, the characteristics of what those rules are, and what the chosen characters are is what creates the family of language, they are the parameters you're allowed to change and must change for it to be a dialect and not just an alternate implementation of the same language.