image There is an argument which is often put forward against the requirement of self-adjointness of the hamiltonian constraint H : Let H be self-adjoint and O be any operator of the form O =[H, A], where A is any operator (many operators that we do not expect could vanish have this form). Then the expectation value of O vanishes on physical states image from image . The mistake in this argument is easily detected by replacing H with a nonrelativistic free particle quantum hamiltonian, A with x, and image with an eigenstate of the momentum: The error is to neglect the infinities generated by the use of generalized states.