QUÆRENS. But was it not a conception of your own mind, a creation of your imagination, or perhaps a reminiscence of your memory? Are you sure it was a reality, not a strange reflection from your memory? [Sidenote: Not a paradox.] LUMEN. That was my first idea; but it was so obvious that I saw before me the Paris of '93, and the events of January 21, that I could no longer be in any doubt about it. Besides, this explanation was anticipated by the fact that the old men of the mountain had preceded me in observing these phenomena, and they had seen, and analysed, and conversed on them as actual facts without knowing anything of the history of our world, and were quite unaware of my knowledge of that history. Further, we had before our eyes _a present fact_, not a past event. QUÆRENS. But, on the other hand, if the past can be thus merged into the present, if reality and vision can be allied in this way, if persons long since dead can be seen again acting on the scene of life, if new structures and metamorphoses in a city like Paris can disappear and give place to the aspect of the city as it was formerly--in short, if the present can vanish and the past be re-created, what certainty can we have of anything? What becomes of the science of observation? What becomes of deductions and theories? On what solid foundation can we base our knowledge? If these things are true, ought we not henceforth to doubt everything, or else to believe everything? [Sidenote: A reality.] LUMEN. Yes, my friend, these considerations and many others occupied my mind and tormented me, but they did not do away with the reality which I was observing. When I had assured myself that we had _present_ before our eyes the events of the year 1793, it immediately occurred to me that science, instead of conflicting with these facts, ought to furnish an explanation of them, for two truths can never be opposed to one another. I investigated the physical laws, and I discovered the solution of the mystery. QUÆRENS. What! the facts were real? [Sidenote: Explanation of the apparent paradox.] [Sidenote: Lumen ascertains the place where he was in space.]