Sigmund Freud (1856-1939)
The three thinkers who influence the Modern Era and Modern literature the most are probably Charles Darwin (1809-1882), Karl Marx (1818-1883) and Sigmund Freud. This is not to say that Modern authors were ardent evolutionists, or Marxists or even practitioners of Freudian psychology; rather, these thinkers simply fueled and framed the perspectives and debates that formulated so much Modern art and literature.
Today, Freud's specific theories are largely dismissed as unscientific. Still, these ideas had a profound influence on art and literature as much as on our common, daily perceptions/conceptions of existence and reality:
The Freudian Legacy:
-- Quite simply, he invents the concept of the subconscious dimension of the mind. That in itself has a profound impact on how we think about thinking, how we think about reality, and how we conceive of our "selves".
-- He puts emphasis on the primacy of that unconscious dimension of our lives; the life of the mind (the "I think" part of Descartes) becomes the central focus; thoughts may actually be privileged over action. Our "truer" selves exist on a different plane than our active and conscious selves (note the Platonic basis of this idea).
-- Thus, things are not as they appear: the truth exists below the surface and is not readily empirically observable: truth reveals itself thru complex, abstract symbols and perverted actions. This emphasis on symbolism will have an especially strong impact on art and literature.
-- Arguably, Freud deepens the Rousseau-an emphasis on the primacy of the individual (vs. society). Freud makes focusing on one's own mental and physical health is a valid and privileged pursuit. We should take ourselves seriously and invest our time in ourselves; we should think of others as equally valuable individuals. This legacy continues to a degree in modern psychoanalysis: we are there to find our "true" selves, those selves perverted by society and our environment. This "self" may also be more important of "valid" than one's social, group life.
-- Further, deepening emphasis on validity of confession as a means of truth (note/remember how this relates to Catholic confession as a means towards absolution of one's "sins"; both Rousseau and Freud discard the religious element of "sin" but main the cathartic element of confession).
-- Dreams as a repository of deep and privileged truth; dreams return to the Western Civilization spotlight after being either banished or ignored by the culture for two thousand years. "They are pyschical [psychological] phenomena of complete validity -- fulfillment of wishes."
-- Dream meaning revealed through symbolism. This symbolism is abstract and meaning is displaced; no simple, straightforward, one-to-one relationship between the symbol or "sign" and what it symbolizes or "signifies".
-- Put all this together, and we find in many ways the basis of the modern novel, modern poetry, and modern art. Art should:
a) focus on individuals; show how the individual is in conflict with society
b) focus on the "inner lives" of those individuals as they struggle to find their truer selves
c) use symbols, and symbols that are vague, opaque and complex, perhaps ambivalent, like a dream
d) privilege characters who achieve a truer self; reconcile the subconscious and conscious "lives" of characters.
Example: Kurtz, Heart of Darkness
Other, perhaps less relevant contributions:
-- Further separation of the individual; further Cartesian splintering of the unified self. Descartes separated/divided the mind from the body (I think (mind); therefore I am (body, existence)) or continued the Western conception of the spirit or soul (thinking, consciousness) as separate from the corporeal body. Freud breaks this down even further, so that thinking/the mind is itself splintered or separated into various elements.
-- Sidelines Descartes Radical Skepticism (Inductive Reasoning) and Empiricism (Scientific emphasis on observable, measurable fact) and sends the field of psychology skiddering off into Platonic/Aristotelian/Religious Deductive Analysis. The mind becomes an abstract place and Freudian theories based on analyses and abstract, logical speculation vs. focus on that which can only be readily observed, measured, quantified, tested and verified. In other words, like Marx, Freud isn't really "doing science" the way someone like Darwin was; this, in my opinion, explains whyFreud is now fairly universally discredited ...but his theories remain a major element of how our culture conceives of the self and mind.
-- Mix of Platonic Idealism, Lockean Empiricism, Rousseauean Romanticism: Our subconscious minds and ideas are our true selves, while our conscious minds are formed thru experience and sensation. As with Rousseau, society may corrupt this truer self, and the individual has a right to return express and perhaps become/return to that self.