Emmanuel Kant, the eminent 18th century German moral philosopher, believed that there was only a single ‘categorical imperative’ in the moral realm: ‘Act only according to that maxim whereby you can, at the same time, will that it should become a universal law.’ Kant believed that only reason, because it is universal and impartial in its application, could tell us the truth about the world and what is correct behaviour. Reason also requires that we ‘treat humanity, whether in your own person or in another, always as an end and never as only a means’ (https://www.britannica.com/topic/categorical-imperative). Behaviour that does not fall within the categorical imperative fails ‘to achieve the minimum of moral worth required to be permissible – not contradicting themselves. The perpetrators have made themselves beastly, subhuman, and relinquished part or all of their dignity. If their misbehaviour should be a crime, then it is perfectly reasonable to consider them, as rational self-legislators, to be authorizing the same treatment against themselves. It is the only way to respect their autonomy and to treat them as an end in themselves and not merely a means.’
