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This work explores the foundations of a deeply felt intuition that pervades American jurisprudence: the act-omission distinction ("AvO"). I conclude that Hume's understanding of the origins of our conception of duties presaged an important insight from modem evolutionary theory: our tendency to engage in altruistic conduct begins, although it clearly does not end, with the physical reality of personal kinship in an unkind world, and it tends to extend out in a social network of ever-diminishing strength the farther we move from the nuclear family. The thesis begins with the observation that we privilege "acts" over "omissions" for purposes of accountability, because the "psychological constituents of human ... nature, like the anatomical and physiological elements thereof, exhibit adaptive design for the solution of particular recurrent problems faced by our ancestors." Given the fact that we are still freighted with a million year old genotype, we should not be surprised that we continue to find it easier to help individuals close to us than perfect strangers and, in either case, especially easier to give aid if the individual is close at hand. Accountability for omissions tends to arise as a function of relationally proximate networks, and among the salient variables that detennine the expectations within these networks are, in the first instance at least, kinship and the power-knowledge imbalances that often exist among individuals in trusting and entrusting relationships. Thus our parents and siblings and our lawyers and doctors and priests have duties to aid that even our best friends do not have. I argue that these variables and, in particular, our largely ineradicable biological commitment to those who are in close familial relationships, are grounded initially in our genetic ties and thus favor our individual natural histories. Overcoming the traditional reluctance to impose duties to act on behalf of third parties will require some remodeling of our social norms.

I hope to demonstrate these points in several steps. Part I removes some of the underbrush with a brief vignette that sets the distinction between acts and omissions as sources of duty and accountability in a plausible hypothetical setting. The purpose of this section is simply to dissect the apparent moral obtuseness of AvO in terms of legal "causation." It concludes, as many others have, that omissions that produce non-trivial harms can be as fully responsibility-engendering as are dynamic acts that cause harm. Thus, to label the conduct in question a "mere omission" is to make a judgment about the culpability of the individual; it is not a statement about material causation. This is not a matter of ambiguity in the term "causation"; rather, it speaks to our intuitions about the propriety of accountability for failing to render aid.

Part II puts the issue of liability based on duties in its contemporary perspective. It thus begins with a summary of the legal concept of "duty," the existence of which is a necessary condition for omission liability. The recognition of a legal duty begins (and ends) with an assessment of status relationships, which are defined by contexts where, as a matter of long term survival, there are and always have been situations in which power, trust, and knowledge imbalances exist. In particular, recognition of a duty occurs where there is a first-order ( or other close) kinship relationship (i.e., spouses, parent-child, child-child, and sometimes child-parent) that requires the superior party to aid the weaker party to assure survival. Part II then outlines several of the principal assumptions of evolutionary theory, and some basic behavioral genetic and neuroscientific data on the anatomy of moral decision-making, and ends with a discussion of selection, the creation of memory, and the satisfaction of pre-existing duties. What I suggest is that over the vast expanse of human history, the imposition of a duty has its roots in a genotype that extends back to the Pleistocene era and our subsequent neurobiological development-in short, its foundation lies in a family social network. As family relationships have become more attenuated over time, duties have been imposed on other trusted surrogates.

There are many conditions that circumscribe our behavior, a point made in Part III, which ties these neurobiological findings to the naturalistic moral psychology of Hume, whose insights support our tendency to impose responsibility based on certain omissions that cause harm. Part III draws together the several strands into a naturalistic account of the intuition that produces AvO and ties those intuitions to the social network that helps to account for AvO. Part IV highlights the Humean framework, puts it into a social network analysis, and offers some observations about the future of AvO and the possibility of remodeling our public norms so that a duty to rescue when we can do so without unreasonable effort becomes an implied term in the social contract because everyone's children are entitled to civil treatment and respect.