The other creature engendered by the problem of knowledge is Lotze's "hypothetical animal." More solitary than the statue that smells roses and at last becomes a man, this animal has but one sensitive spot on its skin, on the end of an antenna and therefore movable. The structure of this animal prevents it, as one can see, from receiving simultaneous perceptions, but Lotze believed that the ability to retract or project its sensitive antenna was enough to allow the all-but-isolated animal to discover the outside world (without the aid of Kantian categories) and to perceive the difference between a stationary object and a mobile one. Vaihinger admired this fiction; it is contained in the work titled Medizinische Psychologie, published in 1852.

--the Book of Imaginary Beings, Jorge Luis Borges (1967)