Ontology work of Tony Fry is important. René Descartes, with "je pense donc je suis" or "cogito ergo sum" or "I think, therefore I am", argued that "the self" is something that we can know exists with epistemological certainty. Descartes argued further that this knowledge could lead to a proof of the certainty of the existence of God, using the ontological argument that had been formulated first by Anselm of Canterbury. Certainty about the existence of "the self" and "the other", however, came under increasing criticism in the 20th century. Sociological theorists, most notably George Herbert Mead and Erving Goffman, saw
Cogito, ergo sum As a critic of Cartesian subjectivity, Heidegger sought to ground human subjectivity in death as that certainty which individualizes and authenticates our being. As he wrote in 1927: "This certainty, that "I myself am in that I will die," is the basic certainty of Dasein itself. It is a genuine statement of Dasein, while "cogito sum" is only the semblance of such a statement. If such pointed formulations mean anything at all, then the appropriate statement pertaining to Dasein in its being would have to be "sum moribundus" [I am in dying], "moribundus" not as someone gravely ill or wounded,