What are the conditions for permitting the unlawful due to necessity?

One of the agreed-upon principles in Islamic law is "Necessities permit the prohibited." Necessity is defined as that which causes harm to a person by its abandonment, and this harm affects the five essential needs (religion, self, honor, intellect, wealth).

For a prohibited act to be permissible due to necessity, two conditions must be met: 1. Compulsion to this specific prohibited act, such that there is nothing else to avert the necessity. 2. That the necessity is actually averted by this prohibited act. If it is not averted by it, or if there is doubt, then it remains prohibited.

Examples: It is permissible for a starving person to eat carrion if they fear death and find nothing else, because both conditions are met. It is not permissible to seek healing with intoxicants or blood, because healing is not certain with them, and the necessity may not be averted. It is permissible to drink intoxicants for someone who is choking and finds nothing else and is certain that it will remove the choking. It is not permissible to drink intoxicants to quench thirst, because it only increases thirst and does not avert the necessity.