THE PERCEPTION OF SPACE. (l.) 13

from an acute one. Distance-apart, too, is a simple sensa- tion the sensation of a line joining the two distant points : lengthen the line, you alter the feeling and with it the distance felt. But with distance and direction we pass to the category of sp&ce-relations, and are immediately confronted by an opinion which makes of all relations something toto ccelo different from all facts of feeling or imagination whatsoever. A rela- tion, for the Platonising school in psychology, is an energy of pure thought, and as such quite incommensurable with the data of sensibility between which it may be perceived to obtain. We may consequently imagine a disciple of this school to say to us at this point : " Suppose you have made a separate specific sensation of each line and each angle, what boots it? You have still the order of directions and of distances to account for ; you have still the relative magnitudes of all these felt figures to state ; you have their respective positions to define before you can be said to have brought order into your space. And not one of these determinations can be effected except through an act of relating thought, so that your attempt to give an account of space in terms of pure sensibility breaks down almost at the very outset. Position, for example, can never be a sensation, for it has nothing intrinsic about it ; it can only obtain between a spot, line or other figure and extraneous co-ordinates, and can never be an element of the feeling of the sensible datum, the line or the spot, in itself. Let us then confess that thought alone can unlock the riddle of space, and that Thought is an ador- able but unfathomable mystery." Such a method of dealing with the problem has the merit of shortness. But let us be in no such hurry, but see whether we cannot get a little deeper, by patiently considering what these space-relations are. ' Kelation ' is a very slippery word. It has so many different concrete meanings that the use of it as an abstract universal may easily introduce bewilderment into our thought. We must therefore be careful to avoid ambiguity by making sure, wherever we have to employ it, what its precise meaning is in that particular sphere of application. At present we have to do with space-relations, and no others. Most ' relations ' are feelings of an entirely different order from the terms they relate. The relation of similarity, e.g., may equally obtain between jasmine and tuberose, or between Mr. Browning's verses and Mr. Story's ; it is itself neither odorous nor poetical, and those may well be pardoned who have