Einstein's response to the question about the nature of future wars reflects a deep concern about the destructive power of modern weaponry. He suggested that while the specifics of the Third World War might be uncertain, its aftermath would lead humanity back to primitive forms of conflict, symbolized by the use of rocks in the Fourth World War. This hints at a catastrophic consequence of technological advancements in warfare which could obliterate civilization as we know it.

Walter Isaacson's biography, "Einstein: His Life and Universe," captures this poignant thought. It underscores the notion that, despite the extraordinary capabilities of modern warfare, fundamental human experiences and conflicts might revert to their most basic forms if civilization collapses. Einstein's foresight serves as a cautionary tale about the trajectory of human conflict and the potential regression to primitive survival tactics.