The 1991 International Convention for the Protection of New Varieties of Plants (UPOV Convention) introduced the concept of “essentially derived varieties” (EDVs) expanding the scope of the plant breeder’s right. The purpose of EDVs was to limit “plagiarism”, “copycat breeding”, “mimics”, “imitations” or “cosmetic” varieties, and an unfair free riding on the original plant breeder’s time and investment. The problem is how to find a measure of difference to distinguish an EDV from a new variety? The presentation addresses why the threshold legal question of EDV is more than a mere quantitative technical question requiring a technical answer, such as a statistical index or a DNA sequence. The answer lies in the sciences of law and the laws of science ... maybe?