Exceptional and diabolical points in stability questions

“I never satisfy myself until I can make a mechanical model of a thing” – guided by this motto of Lord Kelvin we would like to invite a reader to look at some modern concepts such as a non-Hermitian Hamiltonian, exceptional points, the geometric phase, and PT-symmetry, through the prism of the classical mechanics and stability theory. Mathematical and historical parallels discussed in the paper evidence that positions occupied by the non-Hermitian physics and non-conservative mechanics are closer to each other than one might expect.