_Eighth question._--“What is an interval of duration?” It is a relation existing between two opposite terms of succession--that is, between _before_ and _after_. An interval of duration is commonly considered as a continuous extension; yet it is primarily a simple relation by which the extension of the flowing from _before_ to _after_ is formally determined. Nevertheless, since the “when” cannot acquire the opposite formalities, _before_ and _after_, without continuous movement, all interval of duration implies movement, and therefore may be considered also as a continuous quantity. Under this last aspect, the interval of duration is nothing else than the duration of the movement from _before_ to _after_. We have already noticed that the duration of movement, or the interval of duration, is not to be confounded with the duration through which the movement extends. But as, in the popular language, the one as well as the other is termed “relative duration,” we would suggest that the duration through which the movement extends might be called _fundamental_ relative duration, whilst the relation which constitutes an interval between _before_ and _after_ might be called _resultant_ relative duration. The philosophical necessity of this distinction is obvious, first, because the _standing_ duration, through which movement extends, must not be confounded with the _flowing_ duration of movement; secondly, because the relation and its foundation are not the same thing, and, as we have explained at length when treating of relative space, to confound the one with the other leads to Pantheism. Intervals of relation are not _parts_ of absolute duration, though they are so conceived by many, but they are mere relations, as we have stated. Absolute duration is all standing, it has no parts, and it cannot be divided into parts. What is called an interval _of_ duration should rather be called an interval _in_ duration; for it is not a portion of standing duration, but an extrinsic result; it is not a length of absolute duration, but the length of the movement extending through that duration; it is not a divisible extension, but the ground on which movement acquires its divisible extension from _before_ to _after_. In the smallest conceivable interval of duration there is God, with all his eternity. To affirm that intervals of duration are distinct durations would be to cut God’s eternity to pieces by giving it a distinct being in really distinct intervals. Hence it is necessary to concede that, whilst the intervals are distinct, the duration on which they have their foundation is one and the same. The only duration which can be safely confounded with those intervals is the flowing duration of the movement by which they are measured. This is the duration which can be considered as a continuous quantity divisible into parts; and this is the duration which we should style “_resultant_ relative duration,” to avoid all danger of error or equivocation.