information:highlighting
Science and philosophy in the 19th century

Replacing the classical physics in use since the end of the scientific revolution, modern physics arose in the early 20th century with the advent of quantum physics, substituting mathematical studies for experimental studies and examining equations to build a theoretical structure. The old quantum theory was a collection of results which predate modern quantum mechanics, but were never complete or self-consistent. The collection of heuristic prescriptions for quantum mechanics were the first corrections to classical mechanics. Outside the realm of quantum physics, the various aether theories in classical physics, which supposed a " fifth element " such as the Luminiferous aether, were nullified by the Michelson–Morley experiment —an attempt to detect the motion of earth through the aether. In biology, Darwinism gained acceptance, promoting the concept of adaptation in the theory of natural selection. The fields of geology, astronomy and psychology also made strides and gained new insights. In medicine, there were advances in medical theory and treatments.

Starting one-hundred years before the 20th century, the Enlightenment philosophy was challenged in various quarters around the 1900s. Developed from earlier secular traditions, modern Humanist ethical philosophies affirmed the dignity and worth of all people, based on the ability to determine right and wrong by appealing to universal human qualities, particularly rationality, without resorting to the supernatural or alleged divine authority from religious texts. For liberal humanists such as Rousseau and Kant, the universal law of reason guided the way toward total emancipation from any kind of tyranny. These ideas were challenged, for example by the young Karl Marx, who criticized the project of political emancipation (embodied in the form of human rights), asserting it to be symptomatic of the very dehumanization it was supposed to oppose. For Friedrich Nietzsche, humanism was nothing more than a secular version of theism. In his Genealogy of Morals, he argues that human rights exist as a means for the weak to collectively constrain the strong. On this view, such rights do not facilitate emancipation of life, but rather deny it. In the 20th century, the notion that human beings are rationally autonomous was challenged by the concept that humans were driven by unconscious irrational desires.