Martin Fowler is talking about how to improve the productivity of software developers:

An answer I’ve given regularly for many years now, and one that applies to almost anyone who uses a computer, is give them a bigger screen.

These days I say that everyone should have at least two 20 inch screens.

You need more arguments, see the 30-inch Apple Cinema HD Display study, by Pfeiffer Consulting and sponsored by Apple, which states that providing employees with 30-in. computer monitors can boost worker productivity at companies where 17- or 19-in. monitors are typically used (BTW, this study was fiercely criticized by Jacob Nielsen in a recent post titled Productivity and Screen Size).