Neither does Emacs Lisp nor ABCL. Yet they are Lisps by your definition.
> different approach about side effects (-> avoid)
Though not precluded. You can write Clojure with side-effects, but to do so you need to be explicit about it.
> different idea of OOP (-> avoid)
Which says nothing about the language or its Lisp-nature. Clojure has generic dispatch with multimethods, supporting runtime polymorphism. As you say later, "OOP" is meaningless since it's definition is vague, so using this as a reason for Clojure to not be a Lisp is odd.
> Just think of it: zero lines of code is shared.
Are saying that a lisp is only a 'Lisp' if you can freely share code between them? Without modification? If the names used for functions aren't the same, then that disqualifies it from being a Lisp?
Your position seems to be that unless the lisp is a direct descendant of Lisp 1.5 then it cannot be called a Lisp. In addition to Clojure, this disqualifies Scheme (and its dialects.)
Different Lisps (by your definition) take different approaches to things like namespace separation (Lisp-1 vs. Lisp-2) and scope (dynamic vs. lexical). These differences can be subtle and lead to hard to find bugs when sharing code.
> My problem with that broader idea of 'Lisp': it is fully vague and it has no practical implications.
Yet you have put a stake in the ground and defined the broad idea of 'Lisp' as an entity that shares its roots with the ideas in MacLisp.
Neither does Emacs Lisp nor ABCL. Yet they are Lisps by your definition.
> different approach about side effects (-> avoid)
Though not precluded. You can write Clojure with side-effects, but to do so you need to be explicit about it.
> different idea of OOP (-> avoid)
Which says nothing about the language or its Lisp-nature. Clojure has generic dispatch with multimethods, supporting runtime polymorphism. As you say later, "OOP" is meaningless since it's definition is vague, so using this as a reason for Clojure to not be a Lisp is odd.
> Just think of it: zero lines of code is shared.
Are saying that a lisp is only a 'Lisp' if you can freely share code between them? Without modification? If the names used for functions aren't the same, then that disqualifies it from being a Lisp?
Your position seems to be that unless the lisp is a direct descendant of Lisp 1.5 then it cannot be called a Lisp. In addition to Clojure, this disqualifies Scheme (and its dialects.)
Different Lisps (by your definition) take different approaches to things like namespace separation (Lisp-1 vs. Lisp-2) and scope (dynamic vs. lexical). These differences can be subtle and lead to hard to find bugs when sharing code.
> My problem with that broader idea of 'Lisp': it is fully vague and it has no practical implications.
Yet you have put a stake in the ground and defined the broad idea of 'Lisp' as an entity that shares its roots with the ideas in MacLisp.