Following the success of Sony Corporation’s “AIBO”, robot cats and dogs are multiplying rapidly. “Robot pets” employing sophisticated artificial intelligence and animatronic technologies are now being marketed as toys and companions by a number of large consumer electronics corporations. -/- It is often suggested in popular writing about these devices that they could play a worthwhile role in serving the needs of an increasingly aging and socially isolated population. Robot companions, shaped like familiar household pets, could comfort and entertain lonely (...) older persons. This goal is misguided and unethical. While there are a number of apparent benefits that might be thought to accrue from ownership of a robot pet, the majority and the most important of these are predicated on mistaking, at a conscious or unconscious level, the robot for a real animal. For an individual to benefit significantly from ownership of a robot pet they must systematically delude themselves regarding the real nature of their relation with the animal. It requires sentimentality of a morally deplorable sort. Indulging in such sentimentality violates a (weak) duty that we have to ourselves to apprehend the world accurately. The design and manufacture of these robots is unethical in so far as it presupposes or encourages this delusion. -/- The invention of robot pets heralds the arrival of what might be called “ersatz companions” more generally. That is, of devices that are designed to engage in and replicate significant social and emotional relationships. The advent of robot dogs offers a valuable opportunity to think about the worth of such companions, the proper place of robots in society and the value we should place on our relationships with them. (shrink)