Keep it Simple
should be made as simple as possible,
but no simpler
This eventually led to the insight "complex systems break in complex ways". This insight was specific to Information Security and how system complexity has made it virtually impossible to identify flaws and vulnerabilities.
I think there is a parallel insight for large scale programs.
Running such programs over the last decade and a half, it easy to notice that complex program organization typically leads to delays and cost over-runs. So the parallel insight is – breaking the problem into simple parts will allow for simple program organization.
(On a tangential note - see Rule #3 around my take on how keeping it simple is a core principle in building compelling presentations.)