Related to the argument from benefits is the argument from “necessity” or the claim that animal experiments are “essential”: “animal experiments are ‘necessary’; therefore, they are morally permissible.” To evaluate this argument, we must first ask what is meant by “necessary”? There is a sense of the term on which animal experimentation clearly is necessary: to do experiments on animals, it is necessary to do experiments on animals. This is true because to do any exact, particular action, it is necessary to do that action. Whatever is truly meant by “necessity,” an advocate of these arguments assumes a moral premise like the following:
If doing some action is “necessary,” then it is morally permissible.
For some meanings of “necessity” animal experimentation advocates attach to that claim, it will likely be false to say that all, or even much, animal experimentation is “necessary.” For these meanings, this moral principle will have no application.
There are other meanings of “necessary,” e.g., that to say something is “necessary” could be to say that, “it couldn’t be achieved in any other way.” On this meaning, many animal experiments are “necessary.” But, on this meaning, some human vivisection is also “necessary” since some benefits from it also “cannot be achieved in any other way.” The principle above implies such vivisection is not wrong, but it is, so the above principle is arguably false.