Intergenerational equity is often referred to in environmental contexts, as younger age cohorts will disproportionately experience the negative consequences of environmental damage. Two perspectives can be taken on what should be done to ameliorate environmental intergenerational equity: the "weak sustainability" perspective and the "strong sustainability" perspective. From the "weak" perspective, intergenerational equity would be achieved if losses to the environment that future generations face were offset by gains in economic progress. From the "strong" perspective, no amount of economic progress can justify leaving future generations with a degraded environment. According to Professor Sharon Beder, the "weak" perspective is undermined by a lack of knowledge of the future, as we do not know which intrinsically valuable resources will not be able to be replaced by technology. We also do not know to what extent environmental damage is irreversible. Further, more harm cannot be avoided to many species of plants and animals. Other scholars contest Beder's point of view. Professor Wilfred Beckerman insists that "strong sustainability" is "morally repugnant", particularly when it overrides other moral concerns about those alive today. Beckerman insists that the optimal choice for society is to prioritize the welfare of current generations above future generations. He suggests placing a discount rate on outcomes for future generations when accounting for generational equity. Beckerman is extensively criticized by Brian Barry and Nicholas Vrousalis. In September 2015, a group of youth environmental activists filed to sue the U.S. federal government for insufficiently protecting against climate change, the lawsuit is known as Juliana v. United States. Their statement emphasized the disproportionate cost of climate-related damage younger generations would bear. It stated “Youth Plaintiffs represent the youngest living generation, beneficiaries of the public trust. Youth Plaintiffs have a substantial, direct, and immediate interest in protecting the atmosphere, other vital natural resources, their quality of life, their property interests, and their liberties. They also have an interest in ensuring that the climate system remains stable enough to secure their constitutional rights to life, liberty, and property, rights that depend on a livable Future.” In November 2016, the case was allowed to go to trial after US District Court Judge Ann Aiken denied the federal government’s motion to dismiss the case. In her opinion and order, she said, “Exercising my ‘reasoned judgment,’ I have no doubt that the right to a climate system capable of sustaining human life is fundamental to a free and ordered society." As of April 2017, the trial was put on hold with a stay.