What concept did 20th-century philosophies like existentialism respond to?

The correct answer focuses on the response of 20th-century philosophies like existentialism to the profound impacts of scientific technology, particularly in the context of the devastation seen during the world wars. Existentialism arose as a philosophical movement that emphasized individual experience, choice, and the search for meaning in a world increasingly shaped by the consequences of scientific advancements, including warfare and technological destruction.

Philosophers such as Jean-Paul Sartre and Albert Camus grappled with the implications of a world where traditional values were undermined, and where the human condition was marked by trauma and chaos often exacerbated by technology. The existentialist focus on personal responsibility and authenticity was, in part, a reaction to a world where scientific progress had not necessarily led to human flourishing but rather to suffering and disillusionment.

Addressing the other options: While they present various concerns regarding science and rationality, they don't capture the critical existential crisis brought about by the wars, which profoundly altered human perceptions and experiences, leading thinkers to explore themes of absurdity, alienation, and the search for meaning against a backdrop of destruction.