As I read the article, I don't think that's what Fowler was talking about. I think he noticed a trend in things like Less, Sass, Haml, CoffeeScript, etc. The

As I read the article, I don't think that's what Fowler was talking about. I think he noticed a trend in things like Less, Sass, Haml, CoffeeScript, etc. The relationship between, say, Haml and HTML is qualitatively different than the relationship between Clojure and Java (or JVM bytecode). So, it feels like something new is happening and this essay was an attempt to more precisely define an otherwise qualitative feeling. In my reading, here's how he did it. We say a compiler from language X to language Y is transparent when two things are true: 1. The compiler produces a clear and human-understandable mapping between the syntax of X and Y. That is, given code in language X, a human could predict the compiler's output in Y. 2. (1) is not merely a happy accident, but a stated design goal of the compiler or underlying language X. That is, it's not whether (1) is the case, it's whether we're guaranteed that (1) is the case. It's (2) that separates ClojureScript and CoffeeScript. Lots of compilers satisfy (1), e.g., a really naïve C compiler, but it's not by design. There's no intention, no promise to the developer, that the mapping from X -> Y has property (1). For example, ClojureScript's priority is not about producing a clean mapping between Clojure and JavaScript, it's about bringing the expressiveness and power of Clojure to client-side development. If you look at the ClojureScript example page you see lots of "Here's how you do X in ClojureScript, but there's not native way to do X in JavaScript." If we had two ClojureScript compilers A and B, and A produced 10x faster JavaScript than B at the cost of lots of crazy optimizations, we might very well choose A. It'd be a much harder call for CoffeeScript, because part of the pitch CoffeeScript makes to developers is that it's "like JavaScript without all the bad parts." I don't necessarily agree with the above, but that's my understanding of Fowler's argument.