The following text is an abridged English version of a mail I had sent to a vegetarian internet discussion list (vegetarien_fr) on February 4, 2005.
[This person] is, in fact, simply criticising Singer for not sharing his delusional position according to which, by their very principle, it is impossible for experiments on non-humans to have any validity for human medicine. This is the position of Hans Ruesch and many others, unfortunately.
I say it is a delusional position, because that is what it is. I find it hard to understand how anyone with a modicum of common sense could say such a thing. On the basis of this delusional position, it is easy to declare oneself absolutely opposed to all animal experimentation. But of what worth is such opposition? It makes me think of people who would oppose spending money on space missions not on the basis of ethical arguments (that the money would be better spent otherwise, etc.), but on the basis of the Earth being, according to them, flat. If I wanted to oppose these space missions (on ethical grounds), what would I gain by viewing such people as allies? As allies who are even more radical in their opposition to space missions than I am, since their opposition is absolute, based on a factual claim (which is deemed inherently stronger than ethical arguments), etc.? Should I therefore take their arguments on board? I don't think so.
[These people] are very radical, but also very radically delusional. Look, I had already mentioned them in the first issue of the Cahiers antispécistes, more than 14 years ago, which shows how long this has been going on!
Now I come to their rant itself. As I said, it's weird to me that people can believe it, and therefore that we have to respond to it, but there it is. I also see it as the effect of speciesism: because people want to believe that we humans are radically different from other animals, they believe that it would be radically impossible to transpose to humans the results of an experiment on non-human animals.
You can cite as many cases as you like where a product is toxic to parrots, cats or rabbits and not to humans, or vice versa (penicillin, parsley, aspirin, thalidomide, etc.). The fact remains that common sense and daily experience tell us that non-human animals and humans have a similar physiology (more or less similar depending on the animal), and that consequently tests on one have a good probability of being valid on the other.
Imagine that you are lost in the countryside and are thirsty. You come to a place where two rivers meet. You see that the water in both rivers is polluted, each by the waste from a different chemical plant. You hesitate to drink the water, but you are very thirsty. Two dogs arrive; one drinks from the river on the left, the other from the river on the right. The one that drank from the left river collapses and dies in agonizing convulsions. The one who drank from the river on the right goes back quietly as he came. Which river will you choose to drink from?
[These people] would not take into account what they saw, and would drink at random from one or other of the rivers. Even if the banks of the left river are strewn with contorted corpses of not only dogs but also rabbits, cats, parrots, etc., and no corpses are found on the banks of the other river.
H. Ruesch's supporters would not take these findings into account, at least according to what they say. In reality, like everyone else, they would choose to drink from the river on the right, because they know that something that is toxic to dogs is likely to be toxic to humans and vice versa. And they know that all the exceptions they can cite to this general rule are just that: exceptions.
It's strange that those who hold these positions about the radical impossibility of transposing results from one species to another are often also the first to assert the “unity of all life” in other circumstances. Because insecticides are toxic to insects, for example, it seems obvious to them that they will be toxic to humans. They are partly wrong on this point, as insect physiology (in particular, neurotransmitters) is quite different from ours. But on the general principle, they are right: something that is toxic to insects is likely to be toxic to humans. The insecticides that are used are selected from among the rare products that are toxic to insects without being (or rather: while being much less) toxic to humans.
I do not want to go on record as saying that animal experimentation is always “scientifically valid”, nor that it is ethically justified in general. To say that, in the situation of the two rivers, I would take into account the reaction of the dogs does not imply it would be right to force them to drink from the rivers!
On the other hand, I think that a very large proportion of animal experiments are of little or no use. It doesn't cost much (to the experimenters) to poison a hundred rats, and it puts a veneer of objectivity on the results. It often avoids the more perilous and tiring activity of thinking. Much of the criticisms made of the scientific validity of animal experiments has a good deal of truth. This does not imply that all animal experiments are scientifically invalid; and the fact that some experiments are scientifically valid does not in turn imply that these experiments are ethically justified.