Opponents of the use of animals in research challenge scientists and society as a whole to answer a simple question — How can we possible justify harming other living beings in the course of scientific studies?
In framing the moral debate with this question there is an implicit assumption that needs to be clarified. That is, opponents of the research assume that they do not need to provide a moral justification for their own position since they are not the ones harming animals.
However, there are many circumstances where choosing not to act turns out to be untenable.
If we were to find a toddler drowning in a bathtub, we would feel morally obliged to act and to save her life, particularly because doing so would not require us to assume any significant risk to ourselves. Inaction in this case would be morally wrong and unjustifiable. This illustrates the fact that inaction is not morally neutral; it requires justification.
In this regard opponents of animal research are avoiding an important question. What would be the consequence of inaction? That is, what would be the cost to mankind of not doing medical research with animals? And if the answer is that there is substantial cost in terms of lives and suffering, how can one justify not doing the work?
Some research opponents prefer to avoid the question altogether by denying that the research is relevant to human or animal health, implying that harm is done to animals without producing any benefits. However, no matter how many times animal activists attempt to rewrite medical history the facts are clear. Animal research contributed to the development of vaccines for polio, smallpox, diphtheria, tetanus, whooping cough, measles, rubella, mumps, hepatitis A/B, influenza, rotavirus, chickenpox, meningitis, human papillomavirus, all of which combined saved billions of human lives. Animal research also played an important role in the development of antibiotics, blood transfusion, lung surfactants for neonatal care, insulin, antidepressants, anti-retroviral therapy, and so on. The scientific consensus indicates that animal research is critical at the present time to advance medical research and human health. Arguments along these lines fail.

On the other hand, if one accepts the immense benefits of the work to the health of animals and humans alike, then the only way to oppose it is by arguing the case that all living beings have the same basic rights. Certainly, if a mouse has the same rights to life and freedom as a human being, we would not experiment on the mouse for the same reasons we do not experiment on healthy humans. But the overwhelming majority of opponents of research are reluctant to argue the case for animal rights, retreating to the anti-science argument described above instead of explaining clearly to the public why is that a mouse has the same rights to life and freedom as you and me.
If society is being asked to stop doing the research, the least we can expect is a clear and strong moral argument why all living beings deserve same rights to life and freedom accorded to human beings. It is evident that, so far, animal rights philosophers and activists have failed to persuade the public. For those who are frustrated by this failure, we also note that harassment, threats and intimidation do not count as moral arguments either.
When one walks through the halls of a hospital and sees the myriad of patients and the suffering that they and their families experience; and when we further recognize that we have the scientific ability to reduce and eliminate suffering from the world with our work, it adds a dimension to this debate. Suddenly it is the opposition who has the burden of explaining why it would be morally permissible to stop the work that has produced, and will continue to produce, immeasurable benefit to both animals and humans alike.