(ae 
1907-8.] SPACE AND Its DIMENSIONS. 337 
as a grey, and the shaft as a black surface, that is if they are homogeneous. 
If they are not, then you see different distances. The approximately 
lightless shaft, it is true, is much “‘blacker’”’ than an ordinary so called 
black surface on which you still can see the shadows. But if one does not 
correct that which is actually perceived by that which one claims to 
“know,” it appears perfectly surface-like. I have convinced myself of 
this once by an experiment made as a kind of a joke on the occasion of 
one of those illustrated social functions which we have at least once 
every winter at the University of Toronto. For the benefit of some 
artists among the guests I had exhibited a number of different intensities 
of the achromatic series atranged in a plane. The brightest one was a 
good white paper, then came several greys, then a black paper, then black 
velvet, and the last was an aperture into an approximately lightless 
space. This opening was as much different from the black velvet as the 
latter was from the black paper.* I offered one hundred thousand 
dollars to the artist who would produce with oil or water colours on canvas 
or paper, this series in its correct intensity relations. The greater number 
of the spectators did not understand the problem at all, they found it 
beneath their dignity to consider the question which could of course only 
be a “‘language trick.” If they are painters I suppose they are the kind . 
who paint the rising sun so realistically that it could just as well or better 
represent a plate on a cupboard shelf. But many who found it worth 
while to examine the case took the dark opening for some kind of better 
velvet and were greatly startled when on attempting to touch the apparent 
black surface they found no resistance. Nobody without being aided 
by the sense of touch could perceive that it was not a surface but an open- 
ing into an empty space. If we look into a transparent liquid or into a 
fog we see either the irregularities, the deviations from homogeneousness 
(in the case of the fog in the whole mass, in a transparent medium perhaps 
only at the surfaces which form the interior and posterior boundary), 
or we see a homogeneous surface. Hering is quite correct in stating that 
in such cases sufficient indications of certain depths are not entirely lack- 
ing, but even if they are lacking completely we see in this surface as in the 
case of every other surface not a surface in no distance but one in an 
ndefinite distance. 
The theories which claim that two dimensions are given and the third 
one is gained by means of inference will scarcely be able to face the ques- 
tion: can one perceive a surface without seeing it in some, though perhaps 
indefinite, distance? Suppose the originally given space of vision be a sur- 
* See also my treatise on the esthetical significance of light and color contrast. 
Philos. Studien Vol. VII. pp. 362 ff. and also Laws and Conception of Aesthetic. 
U. of T. Studies, Psychological Series. Vol. I. p 177. 
