In On Doubt, Vilém Flusser refines Martin Heidegger's famous declaration that "language is the dwelling of Being." For Flusser, "the word is the dwelling of being," because in fact, in the beginning, there was the word.

On Doubt is a treatise on the human intellect, its relation to language, and the reality-forming discourses that subsequently emerge. For Flusser, the faith that the modern age places in Cartesian doubt plays a role similar to the one that faith in God played in previous eras--a faith that needs to be challenged. Descartes doubts the world through his proposition cogito ergo sum, but leaves doubt itself untouched as indubitable and imperious. His cogito ergo sum may have proved to the Western intellect that thoughts exist, but it did not prove the existence of that which thinks: one can eliminate thinking and yet continue being.

Therefore, should we not doubt doubt itself? Should we not try to go beyond this last step of Cartesian doubt and look for a new faith? The twentieth century has seen many attempts to defeat Cartesian doubt, however, this doubt of doubt has instead generated a complete loss of faith, which the West experiences as existential nihilism. Hence, the emergent emptying of values that results from such extreme doubt. Everything loses its meaning. Can this climate be overcome? Will the West survive the modern age?