It has been argued for 60 years that there exists a relation between surface tension and surface energy on an unstrained solid, as given by the Shuttleworth equation. It is shown here that the Shuttleworth equation reduces to the definition of surface tension derived from mechanics. Therefore, it provides no additional relation to the physics of surfaces. This derivation also reveals precisely how the misinterpretation of the Shuttleworth equation has arisen, and should thus close the discussion on its applicability.