IT HAS NOW BEEN 70 years, almost to the date (October 29, 1945), since Jean-Paul Sartre gave his famous talk “Existentialism is a Humanism,” published as a book a short time later. Speaking just a few months after the end of the Second World War, the French philosopher was concerned with ascertaining the meaning of human existence, the value and import of our choices and the weight of humanity’s responsibility for its actions. Seven decades after this talk, which came to popularize existentialism as one of the best-known philosophical currents of the twentieth century, with ramifications, for instance, in literature (theater, the novel) and cinema, the time has come to re-evaluate its legacy.

Sartre, writing in the shadow of the atrocities of the war, peered into the significance of our relations to ourselves and to our fellow human beings. Now, at a time of widespread ecological destruction, we need to consider not only human interactions but also our behavior towards other living and non-living entities. The human propensity to look beyond the present moment into the future and the inevitability of social relations led Sartre to declare that “existentialism is a humanism.” But what about our exchanges with other creatures that share the planet with us? What is the role of these beings in existentialism? To put it more pointedly, Sartre established that “existentialism is a humanism;” the question we face today is to determine whether it can also be a posthumanism.

Sartre grounds his existentialism on the distinction between human subjects and mere objects. Objects are created according to a plan to fulfill a specific purpose — in Sartre’s example, a paper knife is designed by a craftsman to cut paper. During most of the history of Western thought, humans were considered to be special kinds of objects: they were objects created by a supreme artisan, God Himself. The notion of the human devised by God is thus comparable to the concept of the paper knife in the mind of its manufacturer.

According to Sartre, 18th century-philosophers did away with the idea of God as the ultimate Being responsible for creation. However, they still held on to the belief that humans were the result of a pre-defined human nature, each individual constituting an instantiation of the universal concept of humanity. Both in the theological paradigm and in the secular worldview of the Enlightenment and post-Enlightenment periods, then, essence precedes existence: each person represents a certain configuration of an essence that was given a priori.

The Copernican Revolution that Sartre is proposing, following the philosophy of Martin Heidegger, is that, in the case of human beings, existence precedes essence. This simple inversion entails a series of momentous consequences, foremost amongst which is the idea that human beings are, at each moment, responsible for their behavior, one that does not follow a pre-given pattern, or, in Sartre’s elegant expression, that humans are “condemned to be free.” Values and principles for action are not prescribed by God or by human nature but need to be chosen at every turn of a person’s life, which renders each of us fully responsible for our decisions that can no longer be blamed on external factors. Contrary to the paper knife, then, human beings are not created for this or that purpose or to act in a certain way. Thrown into an open-ended existence, our essence —who we really are —will be the sum total of all our actions and responses to the circumstances in which we find ourselves.

What is missing in Sartre’s depiction of humankind, as opposed to the realm of material objects? The obvious blind spot in his talk is the rest of the world, namely, those entities that are neither human-made objects built with a certain function in mind, like the paper-knife, nor humans themselves. What is the place of animals, plants, rivers, mountains and deserts in existentialism?

Surely, Sartre cannot claim that animals live only to fulfill a goal pre-established by humans. Formerly considered to have been fashioned by God and, therefore, to have been created, just like humans, by a supreme artisan, where does the death of divinity leave these entities? In the absence of a theologically-inflected scala naturae — a ladder of nature that assigned each being a place in the world, with inanimate entities at the bottom, followed by the different plants and animals and reaching, in its higher echelons, humans, angels and, finally God, the guarantor of the system’s cohesion and the one who defined every being’s telos and essence — other entities become just like humans, defined not by a pre-existing essence but by their very lives.

Sartre’s conspicuous silence about humanity’s co-created beings, emancipated from the role assigned to them by their maker with the death of God, is tied to existentialism’s views on human freedom. If he were pressed on this issue, Sartre would probably defend humanity’s exceptionalism by pointing out that the non-human elements of creation cannot be responsible for their actions because they are not free. But in regarding humans as the only free entities, is existentialism not condemning the rest of the world to chains? Worse still, is human freedom not dependent upon the yoke of plants, animals and all other beings, put at the service of supposedly free human masters?

The question of humanism is, at its core, a question about the non-human, about what distinguishes us from others. Humanism is therefore deeply implicated in what has come to be defined as the “environmental crisis.” It is pertinent to recall that the ancient Greek word from which our modern “crisis” derives, krísis, meant a separation, distinction or election. The environmental crisis is rooted precisely in humanity’s separation from the rest of creation, in our conviction that we are inherently better than the rest.

Sartre’s existentialist humanism strove to liberate us from the shackles of essentialism and to show that humans are, at each moment, independent beings responsible for their choices. The relevance of existentialism today hinges upon whether it can be not only a humanism but also a posthumanism.

“Posthumanism” should not be interpreted apocalyptically here, as what sequentially follows once humans have died out. Nor should it be regarded as hinting at the obsolescence of the human as we know it, to be replaced by better hybrids such as the half-human, half-machine cyborgs or the genetically modified humanoids of science fiction. I understand posthumanism as a moment within humanism that is both a step beyond traditional strands of humanism and, at the same time, a revolution (a turning back) of humanism, returning to a more lifelike conception of what being human means.

I would like to finish, then, with seven thesis of existentialist posthumanism, one for each decade that has passed since Sartre’s talk:

  1. Existentialist posthumanism is a recovery of our humanity, lost in abstract conceptions of human exceptionality.
  2. Existentialist posthumanism moderates the notion of human freedom and autonomy and recognizes human heteronomy, that is, our dependence upon other entities on earth to provide for even the most basic of our needs, such as food and shelter.
  3. Existentialist posthumanism is humble, rejecting a larger-than-life view of the human as master of creation.
  4. Existentialist posthumanism follows on the footsteps of traditional humanism in releasing all beings from essentialism and granting freedom not only to humans but also to non-humans beings; it recognizes each entity’s freedom to be according to its own mode of existence.
  5. For existentialist posthumanism, the existence of all beings precedes their essence.
  6. For existentialist posthumanism, all beings have their own universe.
  7. Existentialist humanism is a posthumanism.