I don't think that "it can be emulated by computers" follows from "intelligence is a purely physical phenomenon".
Even fairly simple quantum systems (which are "purely physical phenomena") cannot be emulated by any classical computer in any meaningful sense, since the computational complexity of integrating the dynamical equations is exponential. Even if we could recruit all the atoms in the known Universe, we still couldn't build a classical computer capable of emulating many simple quantum systems.
Even fairly simple quantum systems (which are "purely physical phenomena") cannot be emulated by any classical computer in any meaningful sense, since the computational complexity of integrating the dynamical equations is exponential. Even if we could recruit all the atoms in the known Universe, we still couldn't build a classical computer capable of emulating many simple quantum systems.