To truly understand the universe, we must first understand the limits of our understanding.

For systems, the analogue of a face-lift is to add to the control graph an edge that creates a cycle, not just an additional node.

理解基础是掌握任何复杂系统的关键。

解析：一心在痛上，便无暇顾及他事。

永远保持好奇心，突破往往就在那里发生。