Abstract: The stress theorem of Cauchy in continuum mechanics concludes that the stress vector acting on each oriented surface through a given point of a configuration of a body depends linearly upon the unit normal that orients the surface, if it depends upon it at all. The existence of this linear transformation confirms the existence of the famous Cauchy stress tensor at that point. Common proofs of this cornerstone theorem are based upon the balance of linear momentum and generally involve an action-reaction lemma and the usual 'tetrahedron argument'. In this talk a different approach is described which emphasizes a variational point of view. In a more general setting, this talk is concerned with those laws of balance in continuum physics which require a volume integral and a corresponding boundary surface flux integral to be equal for all sub-parts of the body.