The first volume of the ›Eléments d'idéologie‹ contains Destutt de Tracy's naturalized »Science des Idées«. His opening question is: What is thinking? The question is answered with a systematic theory of sensibility, memory, judgment, will, time and human existence. Destutt de Tracy developed his position by studying Condillac's sensualism and in a critique of Kant. Intellectual capacities, which are based on sensations, and their perfection, are derived from the properties of bodies and movements as well as from the impact of frequent repetition of the same actions in the context of language and signs. This led to a conflict with the church and state authorities. After 1803 Napoleon began his battle against de Tracy, whom he denounced as an »ideologue«.