 Al-Rāzī’s idea, like Abū l-Barakāt’s, is that notions like all-at-once and gradual are known immediately through sensation. While it is true that time and the now, respectively, provide the basis in reality for our perceptions of things emerging gradually or all-at-once, such a relation must be demonstrated and is not immediate. Since the notions of gradual and all-at-once are immediate, they can provide us with the true nature of what motion is. Having identified what motion is, one can use it then to define time and so explain the gradual and the like.