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More Misrepresentations, Fallacies, and Other Lies. Part II

In order to appreciate the fact that the vivisection activist community relies on fallacies and ignores the rules of critical thinking, one must understand and practice critical thinking. I have previously listed many sources for learning about critical thinking, but because this is so vital to understanding how animal models can and cannot be used in science, I list some here again.

A List Of Fallacious Arguments

The Skeptics Dictionary

The Critical Thinking Community

The Skeptics Society and Skeptic magazine


The Skeptics’ Guide to the Universe



Critical Thinking animations

Science-Based Medicine


Regardless of your background and where you are in your critical thinking journey, you should be able to find at least one of the above helpful. You can also search on your own, as the above is a very partial list.

In More Misrepresentations, Fallacies, and Other Lies. Part I, I addressed propaganda that animal and vivisection activists use. I will again use an essay by Tom Holder of Speaking of Research in order to illustrate the Intact Systems Argument. On March 5, 2012, Holder wrote an essay titled: Understanding Adverse Drug Reactions (ADRs). In this essay he addressed the differences between testing on animals and testing on humans in the form of clinical trials. Holder:

There are several reasons why we require both animal and human clinical trials. Animal research plays three roles in research – understanding, development and safety testing – you need to understand how a biological system or a disease works, then you need to model pathologies in order to develop a treatment, and finally you need to ensure that this new treatment is safe.

This is indeed the standard response to the “why test on animals,” question. The real question however is: “Do animal tests accomplish the above?”

In order to defend the use of animals in the three categories “understanding, development and safety testing,” Holder essentially pulls out the intact systems argument: we must test the drug in an intact system as cell cultures and computers cannot replicate an intact human. I have addressed this argument before and will repeat some of the material from that essay.

The intact systems argument (ISA) (LaFollette and Shanks 1996) basically says that in order to understand and or predict what a drug or disease will do in humans, scientists must study the drug or disease in an intact living system (read: dog or rodent or monkey or some other animal) because in vitro research and computer-based research cannot fully replicate a human system. The beauty of this argument, like most lies, is that it presents a partial truth: in vitro and in silico research currently cannot predict human response with 100% accuracy or even a high enough positive predictive value (PPV) and negative predictive value (NPV) to qualify as a predictive technology. Sadly for the vivisection activist, the intact systems argument is an example, not only of bad science, but also of several fallacies including the fallacy of equivocation and the perfect solution fallacy. First the science.

As I have said many times, empirical evidence contradicts the position that animal models can predict human response to drugs and disease and current knowledge from evolution and complexity allows us to put the empirical evidence in context (provides a theory or framework for the evidence). (See Animal Models in Light of Evolution or any of our articles* for more.) The reason the ISA is appealing is that it makes sense that in order to really understand and or predict what will happen in a living complex system (us) we need to study another living complex system (animals), not chemicals in test tubes. Test tubes don’t have kidneys. This is intuitive and correct in what it affirms but incorrect in what it denies. The problem lies in the fact that your living intact system—your body—is different from my living intact system. Currently, the only intact system that will predict with a very high reliability (a high PPV and NPV) what a drug or disease will do in you is you. Animal models, while intact systems, are in reality differently intact or, to put it more scientifically, differently complex. Therefore, what happens in a mouse does not reliably predict via a high PPV and NPV what will happen in you. The ISA assumes that animal models do predict human response and therefore the ISA fails under even minimal scientific scrutiny.*

Neither does the ISA stand up to logical examination.

The perfect solution fallacy states that a solution is not acceptable because it is not perfect. In vitro and in silico tests, as of this writing, are not perfect so the vivisection activist wants to throw them out and use animals. This is obviously not a helpful attitude as the real question is the same for in vitro and in silico tests as it is for animal tests: “Does this testing method have a high enough PPV and NPV to allow scientists to use it as a predictive test or research method?” If a test does not meet this standard, be it an animal-based test or an in silico test, then the test fails the test of prediction. So, the perfect solution fallacy can be used against almost any biomedical test since a vast majority are not 100% predictive (have a PPV and NPV of 1.0). But some do have a high enough PPV and NPV to justify their use as a predictive test and are so used on a daily basis. The reason the perfect solution fallacy is a fallacy is that a test does not have to be 100% perfect to be used as a predictive modality.

However, in medical science the test does have to meet a certain standard (have a high PPV and NPV, say in the neighborhood of 0.9) to be considered predictive. Currently, animal tests fail to meet this standard as do many in vitro and in silico tests. That is why so many drugs fail late in human clinical trials. Tom Patterson, chief scientific officer at Entelos, likens the current practice of drug testing in humans during clinical trials to making airplanes, trying to fly them, and marketing the one that does not crash. (Hodgson 2001) The pharmaceutical industry really has no idea what these drugs will do until they test them on a lot of people, or more realistically—release them to the general population. But while the animal model fails on the whole, there are in vitro and in silico tests that pass the prediction standard and industry is working on developing more. (It is in their best financial interest to develop predictive technologies as soon as possible.) I know of no animal tests that are predictive but there must some aspect of drug testing where animal testing works, just based on statistics. Note that I am not addressing the use of animals after development for example to test for impurities in vaccines. Animals have been successfully employed for such testing. I list such animal use as “animals as bioreactors” in my classification of how animals are used in science and have stated many times that animal models work in many areas of science.

The reason the ISA is an example of the fallacy of equivocation is because the vivisection activist equivocates on what the standard is. When discussing animal tests, a low PPV and NPV are acceptable but when analyzing in vitro and in silico testing he demands a high NPV and PPV.

Moreover, the future of drug testing appears to be in in vitro- and in silico-based testing in the form of gene-based testing. Animal models are not working, despite genetic modifications, and based on what we know about complex systems, I do not think it is even possible that animal models will ever be a predictive modality for the kinds of human responses one looks for in drug development.* Even other humans fail at this and considering animals and humans are examples of complex systems, we will never be able to make a mouse that resembles a human more than another human does.

In this essay, I have addressed the overall theme in Holder’s essay. In the next essay I will address some specific points in the essay.

*I have published volumes on the prediction argument. For more on the science supporting the above, see:

Are animal models predictive for humans?

Animal models in an age of personalized medicine

The History and Implications of Testing Thalidomide on Animals

An analysis of the Bateson Review of research using nonhuman primates

FAQs About the Use of Animals in Science: A handbook for the scientifically perplexed

Animal Models in Light of Evolution


Hodgson, J. 2001. "ADMET--turning chemicals into drugs." Nat Biotechnol no. 19 (8):722-6. doi: 10.1038/90761 90761 [pii].

LaFollette, Hugh, and Niall Shanks. 1996. Brute Science: Dilemmas of animal experimentation. London and New York: Routledge.


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