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He was Anaximander's instructor and the founder of the Milesian School of Natural Philosophy. He was among the first Western philosophers to look for naturalistic (also known as materialistic) explanations of the universe that did not make use of supernatural or mythical explanations, such as the Greek anthropomorphic deities and heroes. -
He was a pioneer of science, occasionally regarded as the first real scientist, and credited with carrying out the first experiment that was ever recorded in the history of science. He believed that everything began from the apeiron, also known as the "infinite," "unlimited," or "indefinite," rather than from a specific element, like water (as Thales had held). Along with the apeiron, Anaximander proposed endless motion as the starting point for the universe. -
Anaximenes was the first Greek to distinguish clearly between planets and stars in the physical sciences, and he utilized his theories to explain a variety of natural occurrences. Anaximenes is best known for his doctrine that air is the source of all things. In this way, he differed with his predecessors like Thales, who held that water is the source of all things, and Anaximander, who thought that all things came from an unspecified boundless stuff. -
The influential philosophical and religious movement or cult known as Pythagoreanism was founded by Pythagoras of Samos, who was also likely the first person to formally refer to himself as a philosopher (or lover of wisdom). The ancient Greek philosopher Pythagoras (c. 570–c. 490 BCE) advocated a highly regimented manner of life and the idea of metempsychosis in his philosophy, known as Pythagoreanism (transmigration of the soul after death into a new body, human or animal). -
He is arguably the most well-known, most-studied, and most-important philosopher to have ever lived. He came to the conclusion that only a select few are qualified to lead, thereby rejecting the Athenian democratic values in favor of reason and knowledge. Plato promotes a eudaemonistic, virtue-based view of ethics. Eudaimonia, or happiness or well-being, is the ultimate goal of moral thought and behavior, and the virtues are the necessary abilities and attitudes to achieve it. -
He was the first to develop a comprehensive system of philosophy, focusing on Ethics, Aesthetics, Politics, etc. Aristotle highlighted the practical nature of virtue and the fact that the goal of ethics is to improve oneself, not only to acquire knowledge. Aristotle contends that the proper path of conduct is not determined by just implementing the rule, but rather depends on the specifics of a certain circumstance. -
He established the Epicurean school of philosophy in ancient Greece, whose fundamental objective was to cultivate friendship, freedom, and an examined existence in order to achieve a joyful, peaceful life marked by the absence of suffering and anxiety. Epicurus' ethics holds that the only thing that has inherent value is one's own pleasure and that everything else is only worthwhile as a way of obtaining one's own pleasure. -
He is credited with founding the Stoic school of thought, which he established in Athens at the beginning of the third century BC. Zeno thought that in order to live rationally, one must acknowledge the transience of all things and their lack of intrinsic worth. According to tradition, Zeno frequently remarked, "I made a prosperous journey when I was shipwrecked," and by this he meant that, before arriving at Athens, his life lacked purpose. -
His teachings had an impact on the growth of Western Christianity and Western philosophy. Augustine argues that to become righteous, wise and holy in eternity like God, man must seek to grow in virtue, knowledge and love now by submitting his intellect and will, disordered by sin, to God's perfect Charity. -
He was an Italian philosopher and theologian of the Middle Ages (also known as Thomas of Aquin or Aquino). Aquinas holds that we should always act in accordance with our conscience, even if doing so is immoral or has a negative impact. Our consciences are our finest moral compass because there is no way for us to know whether they are right or bad. -
He is among the most significant thinkers in the development of Western philosophy. A "categorical imperative" is a universal ethical principle that states that one should always respect the humanity in others and that one should only act in line with principles that could apply for everyone. This idea forms the foundation of Kant's ethical system. -
He was a liberal-trained American moral and political philosopher. According to Rawls, people (like us) who see themselves as free and equal should be able to accept and support as morally defensible the rules of fairness governing our fundamental social institutions and personal behavior.