An example may perhaps convey what is meant by saying that a fact is a contraction of a period of the duration of matter. Consider red, bearing in mind that, when we are speaking of the fact actually perceived when we see red we must discount the logical implications of our words. Science says that red, the material, is composed of immensely rapid vibrations of ether: red, the fact, we know as a simple colour. Bergson accepts the scientific abstractions in terms of which to describe matter, making the reservation that, if we are to talk of matter as composed of vibrations, we must not say that these vibrations last through a period of time or change by themselves, apart from any memory which retains and so preserves the “past” vibrations. If matter is to be thought of at all as existing apart from any memory it must be thought of as consisting of a single vibration in a perpetual present with no past. We might alter the description and say that this present moment of matter should be thought of as being perpetually destroyed and recreated. Now according to Bergson the red which we know directly _is_ a period of the vibrations of matter contracted by memory so as to produce an actual perceived fact. As matter red does not change, it is absolutely discrete and complex, in a word, logical: as fact it is non-logical and forms a creative process of duration. The difference between matter and the actual fact is made by the mental act which holds matter as it were in tension through a period of duration, when a fact is produced, but which would have had to be absent if there had been no fact but simply present matter. Bergson calls this act memory: memory, he says, turns matter into fact by preserving its past along with its present. Without memory there would be no duration and so no change and no time. Matter, apart from memory would have no duration and it is just in this that it is distinguished from actual fact. It is, however, of course, only by making abstractions that we can say what things would be like if something were taken away which actually is not taken away. Matter never really does exist without memory nor memory without its content, matter: the actual fact can only be described as a combination of the two elements, but this description must not lead us into supposing that the abstractions, matter and memory, actually have independent existence apart from the fact which they explain. Only the actual fact exists and it is not really made up of two elements, matter and memory, but only described in terms of these two abstractions.