Far from being a product of Locke’s philosophical genius, the theory of the divine superaddition of thought to matter is rooted in the discussions about Descartes’ conception of the soul as res cogitans which took place in France and in the Netherlands in the years 1640-1680, from Mersenne to Regius and Bayle. Locke’s historical and theoretical relationship with these sources can be clearly documented, as well as the influence of the superaddition theory in the eighteenth century, mostly in the realm of free-thinking, from Collins to Bolingbroke and above all Voltaire. In the light of this intellectual genealogy, the accusations of materialism, or even Spinozism, frequently levelled against Locke acquire a new significance and are worth exploring again.