Abū Hāmid al-Ghazālī (1058–1111 c.e.) is well known, among other things, for his account, in al-Munqidh min al-ḍalāl (Deliverance from error), of a struggle with philosophical skepticism that bears a striking resemblance to that described by Descartes in the Meditations. This essay aims to give a close comparative analysis of these respective accounts, and will concentrate solely on the processes of invoking or entertaining doubt that al-Ghazālī and Descartes describe, respectively. In the process some subtle differences between them in this regard will be brought to light that are relevant to the comparative issue of the respective solutions at which they arrive. The latter issue will not be touched upon here, although the present discussion is intended as a prelude to a future treatment of that topic.