...when fits of creativity run strong, more than one programmer or writer has been known to abandon the desktop for the more spacious floor.

But I will argue that knowing complete product requirements up front is a quite rare exception, not the norm.

The management question, therefore, is not whether to build a pilot system and throw it away. You will do that. Hence plan to throw one away; you will, anyhow.

The hardest single part of building a software system is deciding precisely what to build.

Systems program building is an entropy-decreasing process, hence inherently metastable. Program maintenance is an entropy-increasing process, and even its most skillful execution only delays the subsidence of the system into unfixable obsolescence.

A scientist builds in order to learn; an engineer learns in order to build.

Design work doesn't just satisfy requirements, it elicits them.