Just because the parameters may be diverse does not mean the rules need to be just as diverse. If I may use the biological analogy again, despite the myriad co

Just because the parameters may be diverse does not mean the rules need to be just as diverse. If I may use the biological analogy again, despite the myriad combinations of DNA base pairs, they are all still translated by a universal genetic code that's simple enough to describe in one table (http://en.wikipedia.org/wiki/DNA_codon_table http://en.wikipedia.org/wiki/DNA_codon_table ). I'm fully aware that a description of Universal Grammar would likely be more complex than this though. The collection of language parameters in a person's head is not the language itself, just like the DNA of an individual is not the species itself. It's the translation of those parameters by a shared mechanism that gives rise to the spoken language. This is where I think your book analogy falls through.