Final answer:
The use of discipline by someone under 18 is a complex issue legal and ethical perspectives. While physical discipline like spanking is practised by some, its legality varies, and deadly force is illegal for discipline purposes.
Step-by-step explanation:
The question of whether an individual younger than 18 years old can use discipline but not deadly force is a nuanced one. This matter falls under the realm of law and child welfare practices. The question is blending concepts of self-defense and domestic discipline and needs clarification. When it comes to self-defense laws, they typically do not restrict based on age; however, the use of force must be proportional to the threat faced. Regarding domestic discipline, while 65% of respondents in an ABC News poll approve of spanking and 50% even practice it on their children, this form of punishment is becoming increasingly controversial. It is important to differentiate between corporal punishment used as discipline and actions that could be classified as abusive or deadly.
Legality of Discipline
Corporal punishment by a parent or guardian is legal in some jurisdictions within certain parameters, but it is hugely contentious and considered abuse by others. Deadly force is universally unlawful when used in the context of disciplinary measures regardless of the age of the individual.