Modernism is such slippery word. In everyday use we consider it to mean things of our contemporary era. In literature, Modernism is a particular movement and aesthetic of the 19th and 20th centuries. It is characterized by realism, cynicism, subjectivity, multiple perspectives, and the power of subconscious forces. Following the tragedies of the world wars, the accepted ideas of art and life came into question. Artists strived to abandon convention and recreate new ways of doing things. This emerged in the form of everything from Picasso's cubism to the allusion-filled poetry of T.S Elliot.
Modernism rests on the ideas of thinkers such as Freud, Marx, and the scientists of quantum mechanics. Rather than viewing the world as certain, controlled, and universal, modernists present a world that is subjective, involuntary, and fragmented by the forces of perspective. This can take many forms, but the key idea is leaving behind the conventional world of the early 1900s Century in favor of a life view that is more complex and less certain.