 There are five important assumptions that underlie virtually all contemporary work on decisional capacity and with which anyone interested in the topic must be familiar. For ease of reference we have named them: (1) inclusivity, (2) decision-relativity, (3) all-or-nothing assessment, (4) value neutrality, and (5) independence from diagnosis. These are supported both by ethical theory and by requirements that law imposes on the ethics of informed consent. A sixth assumption, (6) asymmetry, is fairly widely accepted, but continues to be debated.