Final answer:
Kant's philosophy holds that lying is always wrong as it cannot be universalized and undermines trust in communication, while self-defense aligns with the natural law of self-preservation and can be rationally justified. Both stances are related to the categorical imperative, especially the Humanity Formulation that treats humanity as an end in itself.
Step-by-step explanation:
Immanuel Kant's ethical philosophy is predicated on the concept of duty and universalizability. In considering the consistency of his views on lying and self-defense, it is important to note that strict adherence to truth is viewed as a perfect duty, one that must be followed without exception. To Kant, lying undermines the possibility of trust in communication and, if universalized, would lead to a breakdown in meaningful human interaction, an outcome that is irrational and unacceptable. In contrast, the defense of one's life in the face of unjust aggression is permissible as it aligns with the natural law of self-preservation and does not inherently contradict the rational and universal principles of ethical conduct.
When grappling with the conflict between two perfect duties, such as avoiding harm and never telling a lie, Kant's categorical imperative and its formulations provide guidance. Particularly relevant is the Humanity Formulation, which commands that we treat humanity, whether in oneself or another, always as an end and never merely as a means. Thus, while lying is categorically wrong, self-defense is permissible because it does not treat the aggressor merely as a means but rather responds to a direct threat to one's own innate right to life and health, concepts supported by both rational deduction and natural law theory.