Final answer:
Lon Fuller contended that laws must be purposeful, not based on external mortality, and non-retroactive, aligning with legal philosophies that emphasize the role of law in promoting the common good and ensuring fairness by rejecting retroactive penalization.
Step-by-step explanation:
Lon Fuller highlighted that law must be purposeful, arguing against laws with external mortality and retroactivity. He emphasized that laws should serve secular, non-religious purposes and be designed with the intent to promote public welfare. This aligns with the tradition of legal thinking that laws should be rational and foster the common good. Additionally, the prohibition of ex post facto laws ensures that legislation is fair and people are not unjustly penalized for actions that were legal at the time they were committed.
Furthermore, various philosophical traditions, including those of Aquinas and Blackstone, have asserted the importance of laws aligning with natural law and serving societal objectives. Fuller's assertions resonate with these earlier legal philosophies that also rejected laws that retroactively criminalize actions, underscoring the need for predictability and a forward-looking legal system that fosters liberty and justice.