Final answer:
Immanuel Kant held that reason is essential for ethical progress, serving as the foundation of moral judgment. According to Kant, reason allows us to derive categorical imperatives, essential to establishing a moral society over generations.
Step-by-step explanation:
Immanuel Kant posited that reason is the fundamental principle behind moral judgment and ethical progress. For Kant, reason was the tool that could lead individuals to discover categorical imperatives, which are universal ethical principles that should apply to everyone without exception. Kant's belief in ethical progress through reason implies that he saw it as the very basis of moral judgment. This application of reason was seen as a means to guide humanity towards a moral society characterized by great individual freedom. However, this was not the task for a single individual or generation; Kant believed it to be a societal endeavor that would span across generations, gradually perfecting the moral code.
Applying Kant's theory to the question at hand, the correct answer would be a. Reason is the basis of moral judgment. According to Kant, through the steady application of reason, societies would gradually achieve a state of ethical maturity, allowing for the highest degree of freedom and moral action within the community.