Gaston Bachelard might not appear on the short list of well known 20th century thinkers, but he is however a very interesting and inspiring writer with influence on contemporary thought which is not always recognized. With an interesting combination of epistemology, phenomenology and poetics Bachelard made some very interesting, beautiful and influential remarks about science, space, human psychology and the nature of our encounter with the world. Bachelard's most famous book today is "The Poetics of Space" but many of his other writings remain relevant.
Bachelard was a predominantly preoccupied with epistemology and phenomenology which he laced with understanding related to psychoanalysis. This interesting mixture of theoretical orientations stood at the base of Bachelard's investigations into the human condition.
One example of Bachelard's thoughts in this regard, and an example of his subsequent influence, is his accounts on the psychology of science. He was the first one to suggest the scientific progress has to do with certain modes of thought and perceptions, and not just the accumulation of knowledge. Bachelard's concept of epidemiological break as a point of change in such perceptions will later echo in the highly known works of Louis Althusser and Thomas Kuhn.
Another notable area in which Gaston Bachelard has something important to offer is that of poetics (not always distinct from his writing about science). Bachelards' most famous work in this regard is "The Poetics of Space". In "The Poetics of Space" Bachelard holds a phenomenological study of private architecture and its relations to the "architecture of the psyche". Bachelard attempts to describe the private residence though the poetic conceptions of its different parts (what he calls "topoanalysis"). In other words, in "The Poetics of Space" Bachelard explores the inside of the house as the inside of the human soul. He views the house as "primal universe" of psychological existence and ascribes different meaning to various images relating to home and space in general.