We measure the duration of a second, of an hour, of a day, of a year, because the heavenly bodies are there as points of reference between which we can count. Besides, it is all relative. If the Earth moved twice as slowly, the days would be twice as long, but would be apparently the same. If our calendar were different, it would still be our measure of time, and we should be none the wiser. One may put all the clocks forward or backward by one hour, and all the calendars by one day, one month, or one year, change the reckoning of the centuries, or modify the time system in any way one pleases, but it would not change the real course of nature. The terrestrial days and years do not count in the heavens. The time which can be measured in our own system on the nearest planets, Mars, Jupiter, Saturn, Venus, Neptune, although simultaneous with that which we measure here, is not relative to ours. Time is essentially local. If we did not exist there might be other measures of time, but it would not be time according to our conception. In fact our impressions are relative, there is nothing absolute in time. If we suppress life, the sensation of time disappears, time itself ceases to exist. In empty space, a thousand centuries are no longer than one minute, because they do not exist. It is we who say “yesterday” and “to-morrow.” To nature, everything is “to-day.” Besides, every one of us has had the opportunity of proving for himself that time does not exist when we sleep. To sleep one hour or five hours is the same to us as regards the appreciation of time. Time being purely relative, a sleep of a decillion years would be the same as the sleep of an hour. Renan the philosopher, who expressed this truth, added: “Heaven does not exist; in a decillion years it may possibly exist. Those whom a tardy justice places there will believe that they have died the previous evening. To have been, means to be. Succession is the absolute condition of our mind; but in a material object, succession and simultaneity are confounded. When in the presence of death, we ask whether the night will be long, we are as simple as the child who asks the same question in going to bed, because he loves the daylight in which he plays.” If our thinking monads are associated with these worlds to come, eternity is their empire. Speaking in the absolute, time does not exist. But space exists.