In dualism, ‘mind’ is contrasted with ‘body’, but at different times, different aspects of the mind have been the centre of attention. In the classical and mediaeval periods, it was the intellect that was thought to be most obviously resistant to a materialistic account: from Descartes on, the main stumbling block to materialist monism was supposed to be ‘consciousness’, of which phenomenal consciousness or sensation came to be considered as the paradigm instance.