The caliber of recent discourse regarding genetically modified organisms (GMOs) has suffered from a lack of consensus on terminology, from the scarcity of evidence upon which to assess risk to health and to the environment, and from value differences between proponents and opponents of GMOs. Towards addressing these issues, we present the thesis that GM should be defined as the forcible insertion of DNA into a host genome, irrespective of the source of the DNA, and exclusive of conventional or mutation breeding. Some defenders of the commercial use of GMOs have referred to the scientific work of GMO critics as ``junk science.'' Such a claim is false and misleading, given that many papers critical of both the utility and safety of GMOs have been published in peer reviewed journals by respected scientists. In contrast, there is a dearth of peer reviewed work to substantiate the frequently heard assertions of either safety or utility in GMOs. The polarity, which now characterizes much of the public discourse on GMOs, reflects not simply scientific disagreement, but also disagreement in underlying value assumptions. Value differences strongly affect the assessment of both benefit and harm from GMOs. The concept of substantial equivalence occupies a pivotal position in the GMO risk assessment process that is used in both Canada and the US. A GMO judged to be substantially equivalent to a conventional product - as have all submissions to date - is presumed to be safe enough for commercialization. The conclusion of safety - from both human health and environmental perspectives - should be based on scientific evidence, corroborated by actual experimentation. However, regulators infer safety largely from assumptions-based reasoning, with little or no experimental validation. The judgement of safety because of substantial equivalence is a dubious argument by analogy.