From The Aesthetics of Change
All simple and complex regulation as well as learning involve feedback. Contexts of learning and change are therefore principally concerned with altering or establishing feedback.

From Thinking in Systems - A Primer
Complex systems can evolve from simple systems only if there are stable intermediate forms.

From The Systems Bible
A complex system that works is invariably found to have evolved from a simple system that worked.

From Patterns of Software
In the modern era, we have come to favor simplicity over complexity, perfection over imperfection, symmetry over asymmetry, planning over piecemeal growth, and design awards over habitability. Yet if we look at the art we love and the music, the buildings, towns, and houses, the ones we like have the quality without a name, not the deathlike morphology of clean design.

From Safer C
A central and hard-earned engineering principle in older engineering areas such as mechanical engineering and civil engineering is that simplicity rules.

From The Tao of Business
Keeping things simple is an art. And, as with any art, simplicity needs to be cultivated.

From The ACM Turing Award Lectures
I conclude that there are two ways of constructing a software design: One way is to make it so simple that there are obviously no deficiencies and the other way is to make it so complicated that there are no obvious deficiencies. [C.A.R. Hoare]

From The Way of the Leader
The art of leadership is an art based on simplicity, and all success is rooted in performance.

From Extreme Programming Explained
Simplicity supports courage because you can afford to be much more courageous with a simple system.

From Tao Te Ching
Simplicity in conduct, in beliefs, and in environment brings an individual very close to the truth of reality.

From Simplicity
An expert is someone who has succeeded in making decisions and judgements simpler through knowing what to pay attention to and what to ignore. Simplicity means focused effort. Simplicity is a unification around a purpose.

From Simple and Usable
Simple organization is about what feels good as you're using the software, not what looks logical in a plan.