The form which belongs to facts but not to abstractions Bergson calls “duration.” Duration can be described negatively by saying that it is non-logical, but when we attempt any positive description language simply breaks down and we can do nothing but contradict ourselves. Duration does not contain parts united by external relations: it does not contain parts at all, for parts would constitute fixed stages, whereas duration changes continuously. But in order to describe duration at all we have logically only two alternatives, either to speak of it as a plurality, and that implies having parts, or else as a unity, and that by implication, excludes change. Being particularly concerned to emphasise the changing nature of what we know directly Bergson rejects the latter alternative: short of simply giving up the attempt to describe it he has then no choice but to treat this process which he calls duration as a plurality and this drives him into speaking of it as if it had parts. To correct this false impression he adds that these parts are united, not, like logical parts, by external relations, but in quite a new way, by “synthesis.” “Parts” united by synthesis have not the logical characteristics of mutual distinction and externality of relations, they interpenetrate and modify one another. In a series which has duration (such a thing is a contradiction in terms, but the fault lies with the logical form of language which, in spite of its unsatisfactoriness we are driven to employ if we want to describe at all) the “later parts” are not distinct from the “earlier”: “earlier and” “later” are not mutually exclusive relations.