R.G. Frey, DPhil, Professor of Philosophy at Bowling Green State University, wrote in a chapter titled "The Fear of a Slippery Slope," that appeared in his 1998 book Euthanasia and Physician-Assisted Suicide: For and Against, coauthored with Gerald Dworkin and Sissela Bok:

“Especially with regard to taking life, slippery slope arguments have long been a feature of the ethical landscape, used to question the moral permissibility of all kinds of acts… The situation is not unlike that of a doomsday cult that predicts time and again the end of the world, only for followers to discover the next day that things are pretty much as they were…

We need the evidence that shows that horrible slope consequences are likely to occur. The mere possibility that such consequences might occur, as noted earlier, does not constitute such evidence.”