Competing theories exist for how intergenerational investment projects, such as investments related to global warming, natural resources, energy, etc., should be undertaken. In particular, there are two popular prescriptions: (1) In making intergenerational investments, policymakers should use a zero discount rate; and (2) In making intergenerational investments, policymakers should use the market rate. Neither of these prescriptions is correct. Indeed, using present-value discounting at all is extremely problematic. Instead, the best we can probably do is to adopt a simple algorithm: set certain minimal goals for future generations: clean air; potable water; sufficient energy supplies; a nontoxic environment; etc.; and then analyze the most cost-effective way of achieving those goals.