Final answer:
A Kantian Retentionist might support capital punishment by invoking Kant’s deontological ethics. They could argue that punishment, including the death penalty, treats individuals according to universal moral laws and respects their autonomy by holding them accountable for their own actions.
Step-by-step explanation:
A Kantian Retentionist might defend the assumption that punishment can be good for the person punished by arguing that punishment, such as capital punishment, respects the perpetrator's rationality and autonomy by holding them accountable for their actions. According to Kant’s deontological ethics, morality is grounded in duty and the categorical imperative, which holds that one should act only according to the maxim whereby they can, at the same time, will that it should become a universal law. Punishment aligns with this principle by treating the individual as an end in themselves, giving them the consequences of their actions based on universal moral laws, rather than instrumentalizing them for the sake of happiness or consequence. A Kantian might argue that capital punishment is a form of retribution that the criminal has brought upon themselves by their actions, respecting their capacity for moral reasoning and their ability to make choices. However, it's important to note that this position assumes that the system of justice is impeccable in its ability to dispense punishment fairly and accurately, which is a significant point of contention.