> They don’t have to restart the program on exceptions, because the condition system allows resuming the crashing code from anywhere in the stack after the system has been patched with a fix.

I'm "only" using Clojure (which some shall say is not a proper Lisp) and elisp (which is, well, elisp) but I catch every exceptions (including any yet uncaught ones) and I rarely need to restart the app. I've got an helper function to "restart" the app and I can pass a parameter: reset the state of the app or not (usually I don't and keep working with my current app state). As to the main process: I very rarely need to restart the JVM / get a new REPL.

The whole thing is basically a very, very, very long REPL session.

> A consequence of this way of working is that early in a Lisp project, there may not even be any source code to speak of. Instead, the evolving definition of the system exists only in the memory image of the running process and nowhere else.

Yes but be careful... At times this shall bite you: you've got this function or this new definition of that function that you only had working in the REPL and which is not in source code yet. I typically have tests and I run them, from another process, totally unrelated to the one I'm developing in, that I regularly run (not just when I commit): this helps catch at least the most serious "desynch" issues (where the Lisp source code doesn't correspond anymore to what's in the REPL).

> A Lisp programmer does not need to “switch over” to something else because they are already inside their program process. They never “compile and execute” the code because the code is already running and they edit it by hot-swapping code. They never restart in a debugger because they are already inside their program process and can inspect anything they want.

Yup it's all really very sweet. But really: those are all part of that family of languages and not a kludge added later on to the language.

Some people believe that because they have a console in the web dev tools in their browsers that can execute JavaScript code they've got the same thing as a Lisp. It's not anywhere near close to that.