Two Ways of Thinking About Quantum Field Theory

There are two ways to conceptualize quantum field theory: one approach involves starting with a classical field, quantizing it, and observing the emergence of particles; another perspective begins with particles and various states in Hilbert space to describe different particle configurations, eventually leading to the reinvention of quantum field theory. This reveals that the relationship between fields and particles is bidirectional, allowing for the creation and destruction of different particle numbers within the theory.