<p>Preserving and promoting sustainability is an ethical duty of every human person; each person, alone or united with others, ought to use and protect the world for the benefit of all mankind, including future generations, as demanded by the ethical principles of the universal destination of goods and the duty of personal contribution to the common good. Accordingly, although the immediate purpose of a business is economic, it must be understood, from an ethical perspective, that it should aim for sustainable conduct, that benefits all people affected by the business (stakeholders) and preserves ecology. We argue that sustainability should be, in justice, embodied or considered as an integral part of the corporate purpose of all businesses and guide the rectitude of all corporate actions. Sustainability ought to inspire all business activities as a duty of business ethics. This demands a change from the widespread business model based on promoting the increase of consumption and the unlimited exploitation of human and natural resources solely for economic profit, to a more sustainable one. The existing piecemeal legal mechanisms for implementing sustainability fall short and more needs to be done to develop new legal tools that provide a comprehensive framework to achieve corporate sustainability. A more thorough understanding of sustainability as embodied in corporate purpose would foster the advancement of these new legal techniques.</p>