In the late 17th century, the big names in science and philosophy were Newton and Locke, respectively. Locke wrote that human nature was generally good, that government was for the good of the people, that humans had certain "natural rights" that should not be controlled by governments, and that true knowledge was that which could be experienced. Locke also wrote that personality and beliefs were influenced by the environment in which he or she was raised in. The universe, on the other hand, was sketched by Newton, who brought the ideas of Galileo and Kepler together into the concept of gravitational attraction for all bodies, whether they be stars, planets, or people. Both Newton and Locke had ideas that were extremely influential, and that contradicted the pre-existing models of science and humanity. For their time and for almost 200 years, their ideas were sound and influential to next generations.
Then came the late 19th century. The old ideas of Newton and Locke had been around for 200 years, and were leaving some questions unanswered. The new technology of the 20th century gave rise to questions not even imaginable during Newton's days, and new problems in society couldn't be explained by Locke's writings. Carl Marx developed an economic philosophy that was similar to Locke's in that he believed that humanity without government would be able to control itself. While Locke had proposed limited government, Marx proposed none at all. Sigmund Freud's system of psychoanalysis was also remotely related to Locke - he believed that psychological ailments were physical manifestations of a repression of trauma during childhood, which related to Locke's idea of developmental environment affecting people. Darwin threw a wrench into Locke's idea of natural rights by showing that man had originally evolved from animals - therefore, shouldn't Locke's "natural rights" be applicable to animals, also? The discoveries of sub-atomic particles, or at least the idea that the atom was not stable and indestructible, surfaced in the late 19th century. Albert Einstein came up with theories and formulae that interrelated time with space, something that Newton had said was impossible, and better explained the action of gravity and physics. Most of Einstein's theories were influenced by the new discoveries of radiation and matter-energy, the likes of which could never have been found using equipment available in Newton's time. These new ideas and discoveries were almost directly related to an increase in technology from the antiquated days of Newton and Locke - Marx had histories to study, Darwin had new species that had been located on remote islands, Freud had advances in medicine that said some illnesses had no physical cause, and Einstein had numerous discoveries in physics that led to the need for a new model of the universe. The new universe was complex, even now being completely sorted out. Mankind was equally as complex, having the advantages and problems of a large and intricate brain.
The late 19th century was the first major re-vamping of classical philosophy and science since the days of Locke and Newton. And what a change it was. Newton's ideas of gravity were almost completely thrown out, and Locke's ideas were used as breeding grounds for Communism and psychology. The universe was getting bigger and more complex in scientific circles, as was the human mind in psychological communities. These new theories did not eliminate the old unnecessarily, but were needed to continue to make discoveries in their respective fields - imagine where we would be in medicine if it was still thought that germs were harmless. In a kind of association, it could be said that the theories of mankind and the universe evolved from a simple to a more complex state, with even more complex stages to come.