The philosophy of thought to which most modernist writers adhered is Existentialism.
Existentialism philosophy is the 20th-century philosophy which focuses on the way the humans found themselves existing in the world and the analysis of the human existence. In other words, it refers to the finding the meaning of life through free will, personal, and choice.
Existentialism takes into account the concepts of human nature which is chosen through life choices and without supporting the idea of wealth, honor or pleasure to make life good, social structures and value and so forth.