Note 5 — Chapter xix · AN UNKNOWN SENSE

Inclined as we are—and it could not well be otherwise—to judge all things by our standard, the only one in any way known to us, we attribute to animals our own means of perception and do not dream that they might easily possess others of which it is impossible for us to have an exact idea because there is nothing like them in ourselves. Are we quite certain that they are not equipped, in very varying degrees, for the purpose of sensations as foreign to ourselves as the sensation of colours would be if we were blind? Has matter no secrets left for us? Are we so very sure that it is revealed to the living being only by light, sound, taste, smell and touch? Physics and chemistry, young though they be, already declare to us that the dark unknown contains an enormous harvest, in comparison with which our scientific sheaf is the merest penury. A new sense, perhaps that which dwells in the grotesquely exaggerated nose of the Rhinolophus,5 perhaps that which dwells in the antennæ of the Ammophila, would open to our search a world which our physical structure no doubt condemns us to leave for ever unexplored. Cannot certain properties of matter, which have no perceptible action upon us, find a receptive echo in animals, which are differently equipped?