The external events which we see appear to fall into our own local time-succession; but in reality it is not the events themselves, but the sense-impressions to which they indirectly give rise, which take place in the time-succession of our consciousness. The popular outlook does not trouble to discriminate between the external events themselves and the events constituted by their light-impressions on our brains; and hence events throughout the universe are crudely located in our private time-sequence. Through this confusion the idea has arisen that the instants of which we are conscious extend so as to include external events, and are world-wide; and the enduring universe is supposed to consist of a succession of instantaneous states. This crude view was disproved in 1675 by Römer's celebrated discussion of the eclipses of Jupiter's satellites; and we are no longer permitted to locate external events in the instant of our visual perception of them. The whole foundation of the idea of world-wide instants was destroyed $250$~years ago, and it seems strange that it should still survive in current physics. But, as so often happens, the theory was patched up although its original \Foreign{raison d'être} had vanished. Obsessed with the idea that the external events had to be put somehow into the instants of our private consciousness, the physicist succeeded in removing the pressing difficulties by placing them not in the instant of visual perception but in a suitable preceding instant. Physics borrowed the idea of world-wide instants from the rejected theory, and constructed mathematical continuations of the instants in the consciousness of the observer, making in this way time-partitions throughout the four-dimensional world. We need have no quarrel with this very useful construction which gives physical time. We only insist that its artificial nature should be recognised, and that the original demand for a \emph{world-wide} time arose through a mistake. We should probably have had to invent universal time-partitions in any case in order to obtain a complete mesh-system; but it might have saved confusion if we had arrived at it as a deliberate invention instead of an inherited misconception. If it is found that physical time has properties which would ordinarily be regarded as contrary \PageSep{25} to common sense, no surprise need be felt; this highly technical construct of physics is not to be confounded with the time of common sense. It is important for us to discover the exact properties of physical time; but those properties were put into it by the astronomers who invented it. \Section{9.}{The ``$3 + 1$ dimensional'' world}