Aristotle was the founder of virtue ethics, which focuses on the character and habits of the moral agent, rather than on rules or consequences. He also developed the concept of the golden mean, which is the balance between extremes of vice and virtue.
Kant was the founder of deontology, which is the view that morality is based on rational duty and universal principles, rather than on emotions or outcomes. He proposed the categorical imperative, which is a test for the moral validity of any action, based on the idea of treating others as ends and not as means.
Mill was the most influential defender of utilitarianism, which is the view that morality is based on the maximization of happiness and the minimization of suffering for the greatest number of people. He also argued for the principle of liberty, which is the idea that individuals should have the freedom to act as they please, as long as they do not harm others.
Hume was a prominent empiricist and skeptic, who challenged the rationalist foundations of morality and religion. He argued that morality is not derived from reason, but from sentiment and sympathy. He also distinguished between descriptive and prescriptive statements, and questioned the possibility of deriving an 'ought' from an 'is'.
Nietzsche was a radical critic of morality, religion, and metaphysics. He argued that morality is a human construct, and that it serves to oppress and constrain the creative and powerful individuals. He advocated for the idea of theÜbermensch, which is the ideal of the self-overcoming and self-affirming individual, who creates his own values and lives according to his own will.