There is a profound ambiguity surrounding all elements of CIL, particularly as regards the psychological element of opinio juris. This is further accentuated by the prevailing, in international law, elements of absence, silence or non-action and their often-monolithic interpretation as non-objection or, even, acquiescence. But is this true, according to the rules of informal logic? What is the value of non-doing? Non-acting or abstaining? Non-believing towards the formation of a certain opinio juris? The mainstream interpretation of CIL overlooks the quantifications and varieties of meaning in non-appearances, such as the conceivable neutrality of absence. This has led to persuasive-teleological argumentation, in the sense that the person or agency elaborating on either absence or silence aims at a certain end and is thus characterised by a certain ‘argumentative orientation’ towards a preferred conclusion. In this spirit, the ICJ has developed several techniques of superficial, persuasive argumentation, teleologically governed by the non liquet principle, the containment of international crises and the effective resolution of international disputes. This repositions the whole enquiry to the proper place of informal logic in international legal reasoning. The author suggests that an open-system approach could shed light on these inconsistencies and political manoeuvres.