_b_) Suppose a perceived blue surface to be replaced by a perceived red surface--and it will be conceded that the change, or replacement, is also perceived. There is still no ground for a belief in the temporally limited duration of either the red or the blue surface. Anything that leads to this conclusion would lead to the conclusion that the number two ceases when we turn to think of an atom. There is no way then of escaping the conclusion that the adjective "sense" in the term "sense object" is not taken innocently. It is taken as qualifying (for the purposes of statement of the problem) the nature of the object. Aside from reference to the momentariness of the _mental_ event--a reference which is expressly ruled out--there is no way of introducing delimited temporal existence into the object save by reference to one and the same object which is perceived at different times to have different qualities. If the same object--however object be defined--is perceived to be of one color at one time and of another color at another time, then as a matter of course the color-datum of either the earlier or later time is identified as of transitory duration. But equally, of course, there is no question of _inference_ to "other times." Other times have already been used to describe, define, and delimit _this_ (brief) time. A moderate amount of unbiased reflection will, I am confident, convince anyone that apart from a reference to the same existence perduring through different times while changing in _some_ respect, no temporal delimitation of the existence of such a thing as sound or color can be made. Even Plato never doubted the eternal nature of red; he only argued from the fact that a _thing_ is red at one time and blue at another to the unstable, and hence phenomenal, character of the _thing_. Or, put in a different way, we can know that a red is a momentary or transitory existence only if we know of other things which determine its beginning and cessation.