Due to the existence of entropy, exhaustible resources, and resource scarcity, the condition of sustainability as currently conceived seems unlikely ever to be achieved. Nevertheless, Humankind can ensure advancement towards ecologically sustainable development, thereby prolonging the existence of social and ecological stability, by encouraging the proposed inter generational and intra generational equity requirements. The intra generational condition of ensuring equitable access to resources within the current generation will be likely to be a prerequisite to achieving successfully the other equity requirements. A limited time-frame — in which any one generation would only be responsible for meeting the needs of the current generation, and passing to the next generation the resource stocks that they themselves had inherited, or more if possible — has also been proposed to make the pursuit of sustainability a more concrete task, and one that should be more manageable from a policy perspective.