1. Modernity
The ideas and concepts that define modern Western thought emerged in the late 19th century.

2. Applying the principals of science to huge sets of data about societal practices and behaviors, social scientist developed new methodologies and theories to explain their data that went far beyond Enlightenment efforts
The work of Karl Marx falls into this category
August Comte, who initiated the discipline of sociology with his System of Positive Philosophy
Comte argued that intellectual life develops through stages:
The theological or fictitious
Metaphysical or abstract
And finally, the positive or scientific

3. In geology, Charles Lyell established the principle of uniformitarianism, the idea that geological processes slowly formed the earth, not cataclysms like floods or earthquakes.
Lamarck argued that all life forms had evolved slowly adjusting to the environment, although he believed in the inheritance of acquired characteristics
Charles Darwin accepted Lamarck’s basic premise but argued that accidental mutations gave certain members of a species certain advantages in their environment, so that they survived while others without these traits died out. (read PS: Origins of Species and The Descent of Man)
Herbert Spencer applied Darwinism to human society in a doctrine known as Social Darwinism. (PS: Social Statics)

4. Friedrich Nietzsche, a German classical philologist, attacked rationalism and conventional morality as repressive of man’s inner greatness and creative spirit,
and said God was already dead and the only hope was to find individual meaning through personal liberation and exaltation of the individual spirit.
created the concept of the “overman” who would not be bound by traditional notions of good and evil, and would impose his will on weaker individuals.

5. Sigmund Freud is the father of psychology
Sigmund Freud is the father of psychology. His basic premises have become deeply engrained in western society:
That childhood experiences affect our feelings, behaviors, and thoughts as adults
Instincts dominate our unconscious mind
That the unconscious reveals itself in dreams and jokes
and that psychological therapy can help individuals
Freudian terms that are commonly understood and used are ego (self), superego (conscience), id (instinctual drives), repression (pushing into the unconscious) are commonly understood and used.