Suppose that John Doe is an intelligent, sensitive person with one severe neurotic trait - he loves to see living things suffer pain. Fortunately, he never has occasion to torture human beings (he would genuinely regret that), for he can always find an animal for the purpose. For a period he locks himself in his room every night, draws the blind, and then beats and tortures a dog to death.
The sounds of shrieks and moans, which are music to his ears, are nuisances to his neighbours, and when his landlady discovers what he has been doing she is so shocked she has to be hospitalized. Distressed that he has caused harm to human beings, Doe leaves the rooming house, buys a five hundred acre ranch, and moves into a house in the remote, unpopulated center of his own property. There, in the perfect privacy of his own home, he spends every evening maiming, torturing, and beating to death his own animals.
What are we to say of Doe's bizarre behaviour? We have three alternatives. First we can say that it is perfectly permissible since it consists simply in a man's destruction of his own property. How a man disposes in private of his own property is no concern of anyone else providing he causes no nuisance such as loud noises and evil smells.
Second, we can say that this behaviour is patently immoral even though it causes no harm to the interests of anyone other than the actor; further, since it obviously should not be permitted by the law, this is a case where the harm principle is inadequate and must be supplemented by legal moralism.
Third, we can extend the harm principle to animals, and argue that the law can interfere with the harm principle to animals, and argue that the law can interfere with the private enjoyment of property not to enforce "morality as such", but rather to prevent harm to the animals. The third alternative is the most inviting, but not without its difficulties. We must control animal movements, exploit animal labour, and, in many cases, deliberately slaughter animals. All these forms of treatment would be "harm" if inflicted on human beings, but cannot be alowed to count as harm to animals if the harm principle is to be extended to them in any realistic way.
Why must I test on this kind of ickiness?