This paper focuses upon a comparatively overlooked issue with regard to the scope of self-defence in international law: whether the subjective ‘psychological’ positions of the states concerned in a dispute involving the use force have any impact upon the lawfulness of an action avowedly taken in self-defence. There exists a long standing conception that the motives of a state responding in self-defence are relevant to the lawfulness of that response. The purity (or impurity) of a state's motive forms the basis of a distinction for many writers between a lawful self-defence action and an unlawful armed reprisal. Similarly, in recent decisions of the ICJ, the implication has been that the subjective intention of the attacking state may be relevant to the question of whether the attack perpetrated by that state can trigger the right of self-defence. The conclusion is reached here that the lawfulness of an avowed self-defence action should be premised upon objective criteria alone. Moreover, this reflects the law as it is in fact applied in practice. It is argued that the subjective ‘psychological’ position of either the responding or attacking state has no place in the final analysis of whether an action in self-defence was lawful or unlawful.