Decision-Making Capacity

In many Western jurisdictions the law presumes that adult persons, and sometimes children that meet certain criteria, are capable of making their own medical decisions; for example, consenting to a particular medical treatment, or consenting to participate in a research trial. But what exactly does it mean to say that a subject has or lacks the requisite capacity to decide? This question has to do with what is commonly called “decisional capacity”, a central concept in health care law and ethics, and increasingly an independent topic of philosophical inquiry.

Decisional capacity can be defined as the ability of subjects to make their own medical decisions. Somewhat similar questions of capacity arise in other contexts, such as capacity to stand trial in a court of law and the ability to make decisions that relate to personal care and finances. However, the history behind the more general legal notions of capacity to stand trial and capacity to manage one’s life is different and operates somewhat differently in law (Roth, Meisel, & Litz 1977; Zapf & Roesch 2005). For the purposes of this discussion the notion of decisional capacity will be limited to medical contexts only; most notably, those where decisions to consent or to refuse treatment or participation in clinical research are concerned.

This makes sense given that the current notion of decisional capacity in health care arose with, and remains closely tied to, the doctrine of informed consent. Informed consent is both a moral concept and a legal practice that arose in the second half of the twentieth century in response to the widespread paternalism of physicians and clinical researchers. It was only once patients and research subjects began to be involved in making their own decisions that it became clear to many that some sort of fair, formal method was needed for distinguishing between those who can make their own decisions (and so ought to be allowed to) and those who can’t make their own decisions (and so should not be expected to) (Kim 2010: 11–14).

It is fairly obvious that some individuals cannot make their own decisions: persons who are unconscious (temporarily or permanently), individuals with severe brain damage, infants and very small children, those who are born with severe cognitive impairment, and those in the advanced stages of dementia. We do these individuals no favor by pretending that they can decide for themselves. Instead, we must try to look out for these vulnerable individuals in our midst, and to the extent possible, ensure that their perspectives are taken into account in making decisions for them (Silvers & Francis 2009). But these are the “easy” cases. The more difficult task is to develop a fair and consistent notion of decisional capacity that applies to the more subtle cases, the ones in which individuals have some but not all of the mental capacities of ordinary adult agents. It is a moral failure if we say of someone who lacks decisional capacity that she has it, for then we fail to protect someone who genuinely cannot decide for herself. But it is also a serious moral failure to say of someone who has decisional capacity that she lacks it, for we then deprive someone of a very important moral power: the power to direct her own life through making her own decisions (Buchanan & Brock 1989: 40–41; Kim 2010: 1). Those who tackle the issue of capacity face moral danger of various types, and there is no easy way to avoid all moral pitfalls all the time.

Despite the dangers, theoretical questions about decisional capacity remain extremely important because they have huge practical implications. Indeed, it is the combined theoretical and practical nature of decisional capacity that makes it so intellectually compelling to philosophers who write about it. But this is still largely uncultivated philosophical territory. One reason is the highly interdisciplinary and rapidly changing nature of the field. Clinical methods and tests to assess capacity are proliferating even as disagreements remain about whether these instruments track what is truly important. Philosophers have much to contribute, but they must tread carefully if their contributions are to be timely and relevant.