Each unit of time (_kshaṇa_) corresponding to this change of an atom of its own unit of space is the unit-measure of change. This instantaneous succession of time as discrete moments one following the other is the notion of the series of moments or pure and simple succession. Now the notion of these discrete moments is the notion of time. Even the notion of succession is one that does not really exist but is imagined, for a moment comes into being just when the moment just before had passed so that they have never taken place together. Thus Vyāsa in III. 52, says: “_kshaṇatatkramayornāsti vastusamāhāraḥ iti buddhisamāhāraḥ muhūrttāhorātrātrādayaḥ_.” _Sa tvayaṃ kālaḥ vastuśūnyo’pi buddhinirmāṇaḥ._ The moments and their succession do not belong to the category of actual things; the hour, the day and night, are all aggregates of mental conceptions. This time which is not a substantive reality in itself, but is only a mental concept, represented to us through linguistic usage, appears to ordinary minds as if it were an objective reality. So the conception of time as discrete moments is the real one, whereas the conception of time as successive or as continuous is unreal, being only due to the imagination of our empirical and relative consciousness. Thus Vācaspati further explains it. A moment is real (_vastupatitaḥ_) and is the essential element of the notion of succession. Succession involves the notion of change of moments, and the moment is called time by those sages who know what time is. Two moments cannot happen together. There cannot be any succession of two simultaneous things. Succession means the notion of change involving a preceding and a succeeding moment. Thus there is only the present moment and there are no preceding and later moments. Therefore there cannot be any union of these moments. The past and the future moments may be said to exist only if we speak of past and future as identical with the changes that have become latent and others that exist potentially but are not manifested. Thus in one moment, the whole world suffers changes. All these characteristics are associated with the thing as connected with one particular moment.[24] So we find here that time is essentially discrete, being only the moments of our cognitive life. As two moments never co-exist, there is no succession or continuous time. They exist therefore only in our empirical consciousness which cannot take the real moments in their discrete nature but connects the one with the other and thereby imagines either succession or continuous time.