I am by no means a theoretician and I 'get' lisp. I do maintenance and extension on a code base that stretches back to the late 80s. It is a product that runs o

I am by no means a theoretician and I 'get' lisp. I do maintenance and extension on a code base that stretches back to the late 80s. It is a product that runs on windows, has a large user base, and is still gaining customers (though in a decidedly niche market). It appears to me that you do not have very much practical experience writing code in lisp. You are understanding the 'code is data' statement in completely the wrong way. I store and treat my 'data' in exactly the same way that anyone would in perl or python or ruby. I don't think I've ever had a problem distinguishing code from data, when I had the desire. (I keep it in config files, or data files, or in variables). Code is data, to me, means that I can take some data, and transform it into code. Code is a description of how the world is, at some level, and so is data. (For example, I could take a description of the hierarchy of a website's rest service, and write a function to transform it into a series of functions that do the proper requests, in the proper formats, with the proper parsers). How can you argue that lisp does not obey any principles of HCI simply because HCI wasn't invented when Lisp was? It doesn't make sense as an argument. If I don't have a name for something, does it not exist? Gravity didn't exist until Newton described it? What HCI principles does lisp violate? (I find the idea of HCI principles dubious. Isn't good HCI 'whatever scores well in usability tests'). Lisp is not theoretically pure. It is theoretically empty. It makes no assumptions about what the 'proper use' of it is. The whole point of abstraction, to a programmer, is to 'paper over' the actual language and make the program a description of itself. Lisp is amazing at abstraction. (By amazing I mean the unqualified very best). ---- As an addendum. Your comparative usability study[1] is horribly flawed, because you assume programming experience. You should assume no programming experience. The majority of programmers have experience in an Algol derived language. This introduces a huge bias into any study that you would decide to do. Anything that looks and acts like Algol will be easily deciphered, anything else will not be.