Descartes’ metaphysics lays the foundation for the special sciences, and the notion of consciousness (conscientia) belongs to metaphysics rather than to psychology. I argue that as a metaphysical notion, ‘consciousness’ refers to an epistemic version of moral conscience. As a consequence, the activity on which science is based turns out to be conscientious thought. The consciousness that makes science possible is a double awareness: the awareness of what one is thinking, of what one should be doing, and of the possibility (...) of a gap between the two. (shrink)