Preliminaries.- Modular Hilbert algebras.- Generalized Hilbert algebras.- The commutation theorem for modular Hilbert algebras.- Self-adjoint subalgebras of generalized Hilbert algebras.- The spectral algebra.- The modular operator ?.- The resolvent of the modular operator ?.- The one-parameter automorphisms defined by the modular operator ?.- Formulation of the modular Hilbert algebra.- Tensor product and direct sum of modular Hilbert algebras.- The standard representation of von Neumann algebras.- The modular automorphism group and the Kubo-Martin-Schwinger boundary condition.- Semi-finiteness and the modular automorphism group.