One of Śankara's most fundamental claims is that nirguna brahman, ‘unqualified reality’, is the origin of the world of experience. A serious challenge is posed by the Sānkhyan philosophers in terms of a principle of material causation, that the properties manifested in the effect are inherited from the material cause. Since nirguna brahman and the experienced world are so different, the principle implies that the former cannot be the material cause of the latter. Versions of the principle in relation to alternative kinds of candidates for the role of material cause are discussed, considering the particular cases which motivate both Śankara's and the Sānkhyans' metaphysics alike. Śankara seems forced to accept an implausible version of the principle by his own analysis of material causation.