Jeremy Bentham

The day may come when the rest of animal creation may acquire those rights which never could have been with-holden from them but by the hand of tyranny. The French have already discovered that the blackness of the sckin is no reason why a human being should be abandoned without redress to the caprice of a tormentor. It may one day come to be recognized that the number of the legs, the villosity of the skin, or the termination of the os sacrum are reasons equally insufficient for abandoning a sensitive being to the same fate. What else is it that could trace the insuperable line? Is it the faculty of reason, or perhaps the faculty of discourse? But a full-grown horse or dog is beyond comparison a more rational, as well as a more conversable animal, than an infant of a day or a week or even a month, old. But suppose they were otherwise, what would it avail? The question is not, Can they reason nor Can they talk but, Can they suffer? (quoted in AL, 7)

Bentham makes two arguments:

  1. We should not be cruel to animals. (Normative)
  2. Society may acknowledge that we should not be cruel to animals some day. (Descriptive)

Argument I.

  1. We can be cruel to beings that can suffer but can't reason or talk. (assumption for indirect proof)
  2. If can be cruel to beings that can suffer but can't reason or talk, then we can be cruel to infants. (assumption)
  3. Therefore, we can be cruel to infants. (1,2; Modus Ponens)
  4. But we shouldn't be cruel to infants. (assumption; missing premise)
  5. Therefore, either premise 1,2 or 4 is incorrect. (indirect proof)
  6. Therefore, we shouldn't be cruel to beings that can suffer. (reject premise 1)
  7. Animals are beings that can suffer. (assumption; missing premise)
  8. Therefore, we should not be cruel to animals. (6, 7; Universal Instantiation)

Argument II

  1. The French have "discovered" that skin color is no justification for cruelty. (report)
  2. The French are people who recognize sound moral principles. (missing premise)
  3. The rest of the world wants to follow sound moral principles. (missing premise)
  4. Therefore, as go the French, so goes the world. (induction)
  5. .... [left to reader as an exercise (hint: connect to Argument I)]
  6. Therefore, society may acknowledge that we should not be cruel to animals some day.