1907-8.] SPACE AND ITs DIMENSIONS. 333 
memory image may be much more distinct and ntensive than a real 
impression. Thus my memory image of a certain book is much sharper 
and more intensive than the real impression I get of the same or another 
book in the twilight or in indirect vision. Those that hold that direct 
impressions and memory images are only different in intensity will scarcely 
be able to face the following question. Suppose you have a series of 
light sensations, from a very low one, just above the threshold, to a very 
high one, and further that these sensations differ only in intensity. Now 
if the memory image is only different in intensity from the sensation, 
how then can the memory image of a brighter member of the series be 
distinguished from the direct sensation of one of the members of lower 
intensity? On the assumption that the characteristic difference between 
direct impressions and memory images was one of intensity we should 
expect that for instance, a captain on a lake or ocean steamer would 
sometimes be uncertain whether a dim light which he sees at the horizon 
was a real impression or the memory image of a brighter light which he 
had seen before. This difficulty never arises, we are always perfectly 
sure about the distinction of direct impressions and memory images, for 
it is not a matter of intensity or sharpness but one of localization in space. 
The memory image has inner space relations, t.e., space relations of the 
parts to one another, but it has no space relations to the direct impres- 
sions, it is not definitely localized in the vision field except by indirect 
association. Wherever I say ‘‘Here it is.’”-—‘‘There I see it,’ it can be 
answered: ‘‘That is not true, there you see something else.”’ 
The past and the future consist chiefly of memory images, 
and imaginations, sometimes called reproduced elements, though “ repro- 
duced’’ can here mean nothing more than a new state of consciousness 
partly agreeing or identical with a former one. ‘These so-called ‘‘repro- 
duced”’ elements are parts of the present and differ only in the nature 
of their space-relations from other parts of the present, usually called 
direct impressions. Thus the past and the future are matters of knowledge 
(certainty) only in so far as they are parts of the present; all the rest is a 
matter of belief. 
Even if time was, independent of the analogy of space, and inde- 
pendent of the conception of movement into which space and time 
enter, something extended, there would be still no possibility for purely 
temporal series. If variation in the spacial relations of position and shape 
are excluded, a change in a temporal series could only take place in that 
form that where A is first B is afterwards; thus a successive series of 
impressions of sight for instance must at least be localized somewhere 
in space and the impressions must have a spacial magnitude. The ele- 
