This function of the vista as a unifying element is of interest in connection with the theory of Hildebrand,[16] that the landscape should have a narrow foreground and wide background, since that is most in conformity with our experience.  He adduces Titian’s Sacred and Profane Love as an example.  But of the general principle it may be said that not the reproduction of nature, but the production of a unified complex of motor impulses, is the aim of composition, and that this aim is best reached by focusing the eye by a narrow background—­i.e., vista.  No matter how much it wanders, it returns to that central spot and is held there, keeping hold on all the other elements.  Of Hildebrand’s example it may be said that the pyramidal composition with the dark and tall tree in the center effectually accomplishes the binding together of the two figures, so that a vista is not needed.  A wide background without that tree would leave them rather disjointed.

   [16] A. Hildebrand, ’Das Problem der Form in der Bildenden
   Kunst,’ Strassburg, 1897.

Another interesting observation concerns the use of water in landscapes.  In nearly all appears an expanse of water, and in four fifths of the cases it is either on the same side as the vista, or in the same line with it.  This is no doubt partly due to the light-effects which can be got on the water, but it also greatly reinforces the peculiar effect of the vista.  That effect, as has been repeatedly said, is to concentrate, to hold, to fixate vision.  The same thing is true of the horizontal line, as was shown by some preliminary experiments not here reported.  The contrast to the ordinary trend of lines—­particularly in a landscape—­together with the strong suggestion of quiet and repose, serve to give the same concentrating effect to the horizontal lines as to the vista.

In general, it may be said that balance in landscape is effected between Mass and Interest on one side and Vista and Line on the other; and that unity is given especially by the use of Vista and the horizontal lines of water.

A survey of the subject-types remaining on the list of page 514 shows that they may quite well be grouped together with those already examined; that is, the Holy Families, Adorations, Crucifixions, and Annunciations are very symmetrical in type, and present the same characteristics as the Altarpieces.  The Miscellaneous (mostly religious) pictures, the Descents, and the Allegorical are, for the most part, freely composed, irregular, full of action, and resemble the genre pictures.  The Single Figure pictures, Religious, Allegorical and Genre, and the Portrait Groups, resemble the portraits.  Therefore, it may be considered that the existence of a perfect substitutional symmetry has been established, inasmuch as it has been shown to be almost invariably present in the types examined.