Most people are willing to acknowledge that they owe it to themselves to promote their own happiness, to care for their physical health and emotional well being, and to realize their potential as human beings. In some systems of ethics, such responsibilities to oneself are taken as the primary moral duties which all persons have. Self-regarding responsibilities are sometimes thought to arise somehow directly from our nature as rational beings. A basic ethical theory known as ethical egoism proposes that all moral agents owe it to themselves to maximize their own self-interest.
But there is a problem with this view. Duties to benefit oneself are not ordinarily thought of as moral duties, but rather are considered to be matters of prudence. Many moral philosophers distinguish between the demands of morality, which concern what we owe to others, from those of prudence. When speaking about moral responsibilities we are concerned to understand how moral agents should treat others who have wills of their own. But in discussing prudence, one is speaking about how one manages ones own will. One's own will is not generally regarded as an alien will; it is supposed to be under ones own control. Morality is concerned with controlling wills that are alien to ones own will, and so the demands of prudence cannot be moral demands.
The way in which Goodin framed his Vulnerability Principle reflects this distinction between prudence and morality:
(VP): Moral agents acquire special responsibilities to protect the interests of others to the extent that those others are especially vulnerable or in some way dependent on their choices and actions. (Italics added)
As it is stated the VP excludes what I am calling self-regarding responsibilities. I think this is a fundamental problem with Goodin's statement of the vulnerability principle.
So it will be necessary to reformulate the Vulnerability Principle so as to allow these kinds of self-regarding moral responsibilities to fall within its scope. I propose the following re-formulation.
(VCP) Moral agents acquire special responsibilities to care for and protect the interests of moral patients to the extent that those moral patients are especially vulnerable or in some way depending on the actions and choices of those moral agents for their care.
Since moral agents are also moral patients it follows that under the VCP moral agents can acquire special responsibilities to care for and protect their own interests, particularly when they are especially vulnerable or are depending on themselves for their own care or for the protection of their own interests. We can continue to refer to this subclass of moral responsibilities as prudential, understanding that they are now regarded as a special kind of moral responsibility. There are, I believe, situations in which we are vulnerable to ourselves and are also depending on ourselves to protect our own interests. Duties of prudence arise from the VCP, on this view, as a subspecies of the kinds of special moral responsibilities that derive from considerations of vulnerability and dependence to the extent that moral agents are vulnerable to and depending on themselves for their own care and protection.