Upon the whole, it seems the proper objects of sight are light and color, with their several shades and degrees; all which, being infinitely diversified and combined, form a language wonderfully adapted to suggest and exhibit to us the distances, figures, situations, dimensions, and various qualities of tangible objects; not by similitude, nor yet by inference of necessary connection, but by the arbitrary imposition of Providence, just as words suggest the things signified by them. (from Alciphron)