A century after John Goodman, and in a very different intellectual atmosphere, the Enlightenment philosopher Immanuel Kant (1724-1804) sought to establish a complete philosophical system, including a comprehensive system of ethics, by means of rational enquiry alone.
Kant taught science, mathematics and philosophy at the University of Königsberg, and for a time was rector of the university. The city was then the capital of East Prussia but is now in Russia and called Kaliningrad. The university, founded in 1544 as a Lutheran institution, is now named the Immanuel Kant State University of Russia.
In his early thirties Kant expounded, in his General Natural History and Theory of the Heavens (1755), a theory of the origins of the universe. His main philosophical works are from the 1780s and 1790s. In working towards a complete ethical system, he wrote Grundlegung zur Metaphysik der Sitten (1785). The title is variously translated, for example Groundwork for the Metaphysics of Morals or Fundamental Principles of the Metaphysics of Morals. Although this was in some ways a preliminary work, it is extensively quoted, and includes his well-known discussion of practical and categorical imperatives. The former relate to available choices among practical options; the latter are concerned with necessary moral choices, such as not lying or stealing.
Kant propounded a general formula for deciding on categorical imperatives: in moral decision-making a person’s action should be based on a justification which the person would be willing to see as a universal natural law. In other words, do what you think everyone ought to do as a matter of moral obligation. This is a more impersonal way of framing a core moral principle than what we find in the Golden Rule.
Kant discussed the Golden Rule in his Metaphysics of Morals in a footnote. He regarded the Rule as defective, on the grounds that it does not contain (1) a principle of duties that one ought to perform with regard to oneself, (2) a principle of duties of benevolence that one ought to perform to others, or (3) a principle of duties of obligation that one has to others. Since it does not (in his view) require benevolence to others, one can evade showing benevolence to others if one is prepared to allow others not to show benevolence to oneself. With regard to obligation, it might give a criminal a basis for objecting to the punishment which a judge proposes to inflict. For these reasons, in Kant’s view the Golden Rule is incapable of serving as a universal law.
I suggest that there are two main problems with Kant’s analysis of the Golden Rule. First, he complains of what it does not say, without exploring the value of what it does say. Secondly, he fails to take account of a wider setting in which the Golden Rule could be said to belong and which might overcome some of the wariness he expresses about its limitations. For example, if the Golden Rule is considered to operate as a corrective to a principle of retribution, it is given a role which would involve something of the benevolence that Kant thought was lacking. By interpreting the Rule in a strictly literal sense, Kant has missed the nuances and complexities which it may derive from an intended moral setting.
For Kant’s discussion of the Golden Rule, Neil Duxbury, ‘Golden Rule Reasoning, Moral Judgment, and Law’, Notre Dame Law Review 84.4, April 2009, 1529-1605, at p. 1549, quotes Immanuel Kant, Groundwork for the Metaphysics of Morals, ed. and trans. Allen W. Wood, New Haven, Yale University Press, 2002, p. 48.