As Sartre pointed out, philosophical questions are questions that each generation must ask themselves because only this promotes the feeling of being alive, which is especially true for existential questions closely related to time–space, the moment, and our society. Sartre placed his philosophy of existentialism in wartime and the social conditions of the time at the beginning of the 20th century. We can equate these conditions with today’s conditions; we are once again facing threats of war, and once again, we are facing chaotic conditions that increasingly lead to absurdity but are also entirely different. Today, at the beginning of the 21st century, the clarity and disambiguation of the 20th century no longer exist, as the relationships between beings and the world have drastically changed. We can observe that (1) the world is not one; there are two worlds, the physical and the cyber world and (2) being is not one; there are two beings (entities), human and AI-based forms of artificial life (ALF), between which there is a permanent tension. We advocate the thesis that in the society of the future, man must still play a master role; he must still be the being who will guide this society. Also, as Sartre claimed, each era must create its philosophy and consider real time–space. Responses to changes in this time–space also relate to existentialism in the 21st century. In this context, it is necessary to redefine the view of the future and the guidelines for the development of future society.