Which philosopher believed that morality is not derived from the divine but resides in the human soul?

The philosopher who believed that morality is not derived from the divine but resides in the human soul is Immanuel Kant. Kant's ethical framework, known as deontological ethics, asserts that moral principles are grounded in rationality and the inherent dignity of human beings, rather than divine command or external authority. He famously proposed the idea of the categorical imperative, which is a way of evaluating motivations for action and suggests that ethical behavior must be universally applicable.

Kant emphasized the importance of autonomy and the role of reason in moral decision-making, positing that individuals possess an inner moral law that guides their actions. This perspective places morality firmly within the domain of human reason and consciousness, challenging the notion that divine will is necessary for establishing moral values. Kant's views contrast with those of other philosophers, such as John Stuart Mill, who focused on outcomes of actions (utilitarianism), or Friedrich Nietzsche, who critiqued traditional morality, and David Hume, who emphasized feelings and sentiments over rational moral principles.