Humanism is a worldview and a moral philosophy that considers humans to be of primary importance. It is a perspective common to a wide range of ethical stances that attaches importance to human dignity, concerns, and capabilities, particularly rationality. Although the word has many senses, its current philosophical meaning comes into focus when contrasted to the supernatural or to appeals to higher authority. Since the 19th century, humanism has been associated with an anti-clericalism inherited from the 18th-century Enlightenment philosophes. The term covers organized non-theistic religions, secular humanism, and a humanistic life stance.
The term "humanism" is ambiguous. Around 1806 Humanismus was used to describe the classical curriculum offered by German schools, and by 1836 "humanism" was borrowed into English in this sense. In 1856, the great German historian and philologist Georg Voigt used humanism to describe Renaissance Humanism, the movement that flourished in the Italian Renaissance to revive classical learning, a use which won wide acceptance among historians in many nations, especially Italy. This historical and literary use of the word "humanist" derives from the 15th-century Italian term umanista, meaning a teacher or scholar of Classical Greek and Latin literature and the ethical philosophy behind it.
At about the same time, the word "humanism" as a philosophy centered around mankind (as opposed to institutionalized religion) was also being used in Germany by the so-called Left Hegelians, Arnold Ruge, and Karl Marx, who were critical of the close involvement of the church in the repressive German government. There has been a persistent confusion between the several uses of the terms: philosophical humanists look to human-centered antecedents among the Greek philosophers and the great figures of Renaissance history, often assuming somewhat inaccurately that famous historical humanists and champions of human reason had uniformly shared their anti-theistic stance.
Sixth-century BCE pantheists Thales of Miletus and Xenophanes of Colophon prepared the way for later Greek humanist thought. Thales is credited with creating the maxim "Know thyself", and Xenophanes refused to recognize the gods of his time and reserved the divine for the principle of unity in the universe. Later Anaxagoras, often described as the "first freethinker", contributed to the development of science as a method of understanding the universe. These Ionian Greeks were the first thinkers to recognize that nature is available to be studied separately from any alleged supernatural realm. Pericles, a pupil of Anaxagoras, influenced the development of democracy, freedom of thought, and the exposure of superstitions. Although little of their work survives, Protagoras and Democritus both espoused agnosticism and a spiritual morality not based on the supernatural. The historian Thucydides is noted for his scientific and rational approach to history. In the third century BCE, Epicurus became known for his concise phrasing of the problem of evil, lack of belief in the afterlife, and human-centered approaches to achieving eudaimonia. He was also the first Greek philosopher to admit women to his school as a rule.