 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.