How to understand After quantum mechanics, nature itself suddenly became linear?

How to understand Freeman Dyson's Saying:

After quantum mechanics, nature itself suddenly became linear.

• See Freeman Dyson, Birds and Frogs. – Mauro ALLEGRANZA Oct 11 at 10:46
• You tagged the post with linear algebra so you already know about the Hilbert space and matrix formulation (historically as per Heisenberg, as opposed to wave mechanics) and all that. What is your real question? – Lee David Chung Lin Oct 11 at 14:55
• why nature itself became linea? – aircraft Oct 11 at 14:57
• Of course nature didn't change. It is just that our past, nonlinear, ways of understanding nature were replaced by the new, quantum, linear, ways of understanding. – Gerald Edgar Oct 11 at 15:14
• Equations of classical mechanics are non-linear ODE, equations of quantum mechanics are linear PDE, so metaphorically the non-linear classical nature "became" linear at a more fundamental level. – Conifold Oct 11 at 21:54