Harrison (2000) argues that sustainable development can best be understood in terms of postmodern thought, as postmodernism is an abandonment of determinism, certainty, and universality in favor of contingency, relativism, and organism (Best & Kellner, 1997: 6). With “no true path to sustainability” (Harrison, 2000: 99), the movement is more properly considered a “long-term, open-ended project‟ (Kemp & Martens, 2007), that embraces moral pluralism (Gladwin et al, 1995), in which “no single approach will, or indeed should be, seen as the correct one” (Robinson, 2003: 382). Embracing the postmodern perspective, however, may potentially weaken the individual’s motivation to engage with sustainable development.
For the individual in an existential position, a postmodern perspective is of little use. Postmodernism signifies a “breakdown of the order of meaning, where all transcendent claims for a meaning to life have been reduced to mere values, all open to interpretation (Critchley, 1997). In this sense, there can be no “authentic‟ anything, let alone sustainable development, as there is no truth, and any approach is just seen as a different interpretation. In the words of Fyodor Dostoevsky‟s (1821 – 1881), as cited by Crowell (2010) “everything is permitted”. Weak sustainability would be just as valid as strong sustainability, putting the concept of sustainable development at risk of plunging into meaninglessness (Dresner, 2002; Hopwood et al. 2005). This can complicate the creation of sustainable development strategies because of the potentially paralyzing effect of being too skeptical of rationalism.
While the existentialists are also skeptical of objective truth, they differ from postmodernists by trying to seek new meaning and value which is best suited to the human way of relating to existence (i.e. Heidegger‟s existentialism). Like the postmodernist, existentialists challenge rationality and scientism, but an existentialist is neither a rationalist nor an irrationalist. The issue returns to the false premise that the “mind and world are logically independent of one another” (Cooper, 1990: 15). Modernism’s desire for objectivity requires that the world be “stripped of everything which human beings have “projected‟ upon it,” and postmodernism, by contrast, equally attempts to separate mind and world through subjective morality (Cooper, 2002: 15).
Panza & Gale (2008) explain the situation well by relating it to Plato‟s Republic, in which the poets, who communicate through passion, were thrown out in order to create a perfect society based on reason. With the failure or reason in fulfilling its promise, the postmodernists have not only invited the poets back in, but “they put them in charge” (Panza & Gale, 2008). In contrast, existentialism rejects the separation between rationality and human passion and seeks a more holistic framework that better represents “all aspects of humanity” (Panza & Gale, 2008: 301). By understanding human existence phenomenologically, existentialists like Heidegger and Sartre have presented ontologies that accept both rationality and passion; a more authentic and “appropriate‟ approach with a lower likelihood of leading to the paralysis of pluralism and uncertainty or the false legitimation of rational modernism and its risk of nihilism.
In using the term “appropriate,‟ that is not to mean “correctness,‟ which implies that either worldview is right or wrong; instead, appropriateness applies to what is most “authentic‟ in terms of actual human existence and experience (Gladwin et al, 1995). From the existentialist point of view, both modernist and postmodernist approaches to sustainable development can be considered inauthentic because they do not represent a means of living that accurately represents who we are as conscious beings.