Closely related to Worldview/Religious theories are theories such as Immanuel Kant’s (1724-1804). Kant developed a highly influential moral theory according to which autonomy is a necessary property to be the kind of being whose interests are to count direclty in the moral assessment of actions (Kant, 1983, 1956). According to Kant, morally permissible actions are those actions that could be willed by all rational individuals in the circumstances. The important part of his conception for the moral status of animals is his reliance on the notion of willing. While both animals and human beings have desires that can compel them to action, only human beings are capable of standing back from their desires and choosing which course of action to take. This ability is manifested by our wills. Since animals lack this ability, they lack a will, and therefore are not autonomous. According to Kant, the only thing with any intrinsic value is a good will. Since animals have no wills at all, they cannot have good wills; they therefore do not have any intrinsic value.
Kant’s theory goes beyond the Worldview/Religious theories by relying on more general philosophical arguments about the nature of morality. Rather than simply relying on the fact that it is “natural” for rational and autonomous beings to use non-rational beings as they see fit, Kant instead provides an argument for the relevance of rationality and autonomy. A theory is a Kantian theory, then, if it provides an account of the properties that human beings have and animals lack that warrants our according human beings a very strong moral status while denying animals any kind of moral status at all. Kant’s own theory focused on the value of autonomy; other Kantian theories focus on such properties as being a moral agent, being able to exist in a reciprocal relation with other human beings, being able to speak, or being self-aware.