Regulating germ-line gene therapy to avoid sliding down the slippery slope

Many arguments can be made for or against various regulatory approaches towards germ-line gene therapy and its associated research. A popular conclusion is that it ought to be prohibited, and this is commonly defended by use of a slippery slope argument. This paper will begin by outlining the regulatory approaches adopted towards germ-line gene therapy in EU countries, demonstrating the popularity of the restrictive approach. The slippery slope argument will then be examined. A number of variants of the slippery slope argument will be distinguished, highlighting the conceptually different claims made by each. Finally, examples of slippery slope arguments often invoked to support the prohibition of germ-line gene therapy will be examined with regard to the conditions that each must satisfy to form a theoretically sound argument. I will argue that these conditions are rarely given sufficient consideration. For the purposes of this paper, "germ-line gene therapy" is defined as the deliberate genetic modification of germ cells (sperm or oocytes), their precursors, or the cells of early embryos where the germ-line has yet to be segregated.