“The limits of my language,” wrote the philosopher Ludwig Wittgenstein, “mean the limits of my world.”

The languages of today’s complex financial markets often consist not simply of words and numbers but also of technical systems. The credit crisis has shown the importance of their powers – and limits.

Although few outsiders have heard of it, the single most important language of mortgage-backed securities and similar products is a system called Intex. It includes a computer language for defining deals’ intricate cash flow rules, a graphics-based tool for designing deals, and a truly remarkable computerised “library” of the parameters of the underlying asset pools and the cash flow rules of more than 20,000 deals. Intex is not cheap – one user told me his bank pays about $1.5m a year for it – and it has competitors such as Bloomberg, but it is essential for all serious participants in structured securities.