Given the central place organisms occupy in Kant’s account of living nature, it might seem unlikely that his claims about biological wholes could be relevant to current debates over the problem of biological individuality. These debates acknowledge the multiple realizability of biological individuality in vastly different forms, including parts of organisms and complex groups of organisms at various levels of the biological hierarchy, sparking much controversy in attempts to characterize a biological individual. I argue that, far from being irrelevant to this controversy, Kant’s account provides a key insight for addressing the multiple realizability problem. I show how the reciprocal causality between a self-organizing whole and its parts, which Kant thinks characterizes a natural end, is not limited to organisms but is exhibited by numerous types of beings in living nature. Self-organizing wholes of various kinds, and at various biological levels, may count as biological individuals, depending on the degree to which their functionally integrated parts are represented by reflective judgement as a natural end.

Recently, a number of Kantians have argued that despite Kant’s own disparaging comments about same-sex intercourse and marriage, his ethical and legal philosophy lacks the resources to show that they are impermissible. I go further by arguing that his framework is in fact more open to same-sex than to different-sex marriage. Central is Kant’s claim that marriage requires equality between spouses. Kant himself thought that men and women are not equal, and some of his more insightful remarks on the issue reveal that he was also aware that, as a matter of fact, women were disenfranchised by society, and suffer legal and other forms of discrimination. Kant, according to his own account, cannot approve of heterosexual marriage. Same-sex couples, by contrast, can satisfy the crucial equality condition. I conclude with a suggestion for refocus with respect to the issues at hand, calling for attention to more complex and insidious forms of inequality than deprivation of rights and full civil participation.