It will be convenient to suppose that the modifications to which it refers are solely due to the observing mind, as the most conspicuous and comprehensive really are, but some of the minor perspective changes are due to the noumenon of the object. We have first to get a criterion of perspective perfection. What this shall be is to some extent a matter of convention. The standard I shall adopt is, that an object of a nature to be perceptible to all the senses would be most perfect if within reach of touch. If it can be heard it is then heard at its loudest--this is correct enough for our purpose,--if it can be seen it is then seen at its largest and brightest. This is Perspective Completeness at the Tactual Range. It means the closest contact of noumenon and subject, compatible with clear definition in perception. Now let us exert energy and disarrange a group. Those things that were or might have been tangible in the former position, are no longer so, but they may still be seen, heard, or even smelt. The bright colours have however somewhat faded, the size has shrunk, some of the details are lost. Here is a lapse from perspective completeness. It is indicated, not as in the first two categories by mechanical cutting away of mass and circumstance, but by deterioration all over the object. We seem to be thrown out of focus in relation to it, and the perspective degradation may increase until the object has dwindled to a speck and finally disappears altogether. The judgment in this category consists in observing the kind and degree of degradation to which things are liable in perspection. In addition to change in size, brightness, detail and loudness, which have been already mentioned, occultation as in the second category can be used as an indirect datum. An object which eclipses another is invariably more perfect perspectively than the object eclipsed. The motion of objects has also to be taken into account. As objects degrade their movements slacken, and recover power as the objects are restored. By attending to all these indications and checking each by the rest, we have the elements of a fairly accurate inference as to comparative perspective condition. We have constant practice in this sort of thought with frequent opportunities of verifying our conclusions; penalties are annexed to failure and rewards to success. It is no wonder then that in the course of years we become expert in judging of perspective condition, so that when confronted with a natural group we can estimate almost instantly the degree in which each object falls short of perspective integrity.