First of all, look round a room and note the different objects to be seen. Even in a small room we do not see the objects as they really _are_ at this instant, but only as they _were_ at a certain fixed length of time ago. The present time is common to every point in space and each person is in the present, but only to his own perception; to everyone else in the room, each individual is, at this moment, being seen acting in the past; those objects which are further away are being seen further behind in point of time than those that are nearer; in fact, however near we are to an object, we can never see it as it is but only as it was. We are dealing with very minute differences here, they being based upon the rate at which light travels; but they are differences which are known with a wonderful degree of accuracy. We have here another example of how perception without knowledge leads to false concepts. When anyone views an extended landscape, he thinks that his sight shows him that the same point of Time, which he is experiencing, is common to every man, animal, plant, or material visible there, but we know now that he is seeing every part of that scene in the past compared with himself. Just as all objects therein are situated at separate distinct points of space, so to our vision the objects of that scene are acting or existing in different epochs of time. An Artist gives us on a flat surface a picture of that landscape, and his representations of all objects in that scene appear therefore to us as being in the same moment of Time, but to get that effect he has to draw objects at a distance smaller than those close at hand; a fly in the foreground has to be drawn larger than a horse supposed to be in the distance, though both are on the same flat surface; they have the same parallax and are therefore the same distance from the observer, and as this produces a similar image on our retina, we accept it though we know it is only a make-believe; it serves its purpose by giving us an impression on our retina which we have learnt to interpret as representing that landscape, but such a picture would indeed be a marvel of absurdity to a being who had perfect sight, such as we have already referred to, and who could appreciate parallel rays; in such a vision there would be no perspective, no vanishing point in perception.