Modern life support systems can keep an individual's body alive for years, even if that person has no brain activity or is in constant pain.
As competent adults, we have a constitutional right to make decisions about whether or not we want life support to continue when death is imminent or when a coma or vegetative state becomes permanent.
A living will is a document that explains whether or not you want to be kept on life support if you become terminally ill and will die shortly without life support, or fall into a persistent vegetative state. It also addresses other important questions, detailing your preferences for tube feeding, artificial hydration, and pain medication in certain situations. A living will becomes effective only when you cannot communicate your desires on your own.
If you want to create a binding living will, LegalZoom can help.