From the beginning of Descartes’ intellectual career, imagination played a major role in his writings, even when he took pains to point out its limitations and pathologies. This role is more central and apparent to those who have available the entire oeuvre than to his contemporaries. But even contemporary scholarly evaluations are often unduly influenced by the assumption that, in showing imagination's weakness, the Meditations establishes its cognitive insignificance. This assumption can lead to overlooking the fundamental importance of imagination in Descartes’ philosophy.

Although the history of imagination is complex, one can nevertheless identify several intellectual streams influencing the early seventeenth century. Medical, Aristotelian, Platonic, and Stoic traditions agreed in conceiving imagination as a medial psychophysiological power: located midway between the deliverances of the external senses and intellectual conception, in terms of both psychology and physiology (see anatomy and physiology). Humanists regarded it as crucial for adapting knowledge to circumstances; in rhetorical theory, it was decisive for discovering topics and putting them in order. In the mathematical sciences (especially geometry), it played an important role in the transition between thinking natural things in place and thinking mathematical objects in abstract space. Already in late antiquity the greatest Platonist philosopher of mathematics, Proclus, had argued that mathematics required intellectual imagination (Nikulin 2002 and Rabouin 2009).

Descartes was introduced to the Aristotelian conception of imagination by his Jesuit teachers at the Collège Henri IV de La Flèche. Aristotle had argued that in animals the external senses were united in common sensation, and that the sensible forms appearing there (called phantasms or images) could be psychophysiologically preserved and reactivated. Moreover, in human beings, there was no thinking without such phantasms. Muslim philosopher-physicians like ibn Rushd (Averroës) and ibn Sina (Avicenna) and their European Scholastic followers developed from these indications rigorous accounts of the complex activity (physiological as well as psychological) of images in an expanded realm of internal sensation. This activity began in higher animals with common sensation's presentation of a world of sensory appearances; proceeded to the memorative and imaginative powers that retain, reproduce, and recombine the phantasms; and advanced to the instinctive assessment of these representations as noxious or advantageous to the animal, assessments that led to purposive behavior.