This article reassesses the legal character of 'the general principles of law recognized by civilized nations', being one of the two unwritten sources of international law. The general principles of law are, however, the most controversial source of international law and have continued to divide the opinions of scholars and judges alike since their inception. Some view them as private law analogies, others as emanations of natural law and there are those who conflate them with custom. This article seeks to identify the appropriate methodology for ascertaining the existence of the controversial 'general principles of law'. It does so by going back to the preparatory works of Article 38(1)(c) of the Statute of the International Court of Justice and then critically assessing the practice of states and the case law of the Court on identifying general principles. It will be argued that general principles of law are an important source of international law in their own right with a systemic function in the international legal order and a distinct methodology for their ascertainment. Three categories of general principles will be distinguished based on the nuanced methodologies for their ascertainment applied by the International Court of Justice and its predecessor, namely, general principles of international law, general principles of domestic law and general principles of procedural law.