The interaction of a ’’scalar’’ charge es (even under T) and a ’’pseudoscalar’’ charge ep (odd under T) is investigated in the framework of classical mechanics. We show that the most general force consistent with the conservation of linear momentum and angular momentum is F=esep(r×v)/cr3, where c is a constant. This is just Dirac’s force between electric and magnetic charges. No use is made of Maxwell’s equations. With the single assumption that the forces can be expressed in terms of vector and axial vector fields, we can derive exact expressions for the fields and then for the forces between two scalar and two pseudoscalar charges. These forces, in turn, are found to be identical with those of Coulomb and Biot–Savart. The theory retains P conservation and T invariance in both Newton’s laws of motion and the expressions for the fields.