In essence, Joiner proposed that people who kill themselves must meet two sets of conditions on top of feeling depressed and hopeless.
First, they must have a serious desire to die. This usually comes about when people feel they are an intolerable burden on others, while also feeling isolated from people who might provide a sense of belonging.
Second, and most important, people who succeed in killing themselves must be capable of doing the deed. This may sound obvious, but until Joiner pointed it out, no one had tried to figure out why some people are able to go through with it when most are not. No matter how seriously you want to die, Joiner says, it is not an easy thing to do. The self-preservation instinct is too strong. There are two ways people who want to die develop the ability to override the self-preservation instinct, Joiner argues. One is by working up to it. In many cases a first suicide attempt is tentative, with shallow cuts or a mild overdose. It is only after multiple attempts that the actions are fatal.
