In the Apology of Socrates, after Socrates is sentenced to death, he addresses the court. He ponders the nature of death, and summarizes that there are basically two opinions about it. The first is that it is a migration of the soul or consciousness from this existence into another, and that the souls of all previously deceased people will also be there. This excites Socrates, because he will be able to conduct his dialectic inquiries with all of the great Greek heroes and thinkers of the past. The other opinion about death is that it is oblivion, the complete cessation of consciousness, not only unable to feel but a complete lack of awareness, like a person in a deep, dreamless sleep. Socrates says that even this oblivion does not frighten him very much, because while he would be unaware, he would correspondingly be free from any pain or suffering. Indeed, Socrates says, not even the great King of Persia could say that he ever rested so soundly and peacefully as he did in a dreamless sleep. Cicero, writing three centuries later in his treatise On Old Age, in the voice of Cato the Elder, similarly discussed the prospects of death, frequently referring to the works of earlier Greek writers. Cicero also concluded that death was either a continuation of consciousness or cessation of it, and that if consciousness continues in some form, there is no reason to fear death; while if it is in fact eternal oblivion, he will be free of all worldly miseries, in which case he should also not be deeply troubled by death. Similar thoughts about death were expressed by the Romanpoet and philosopherLucretius in his first-century BC didactic poemDe rerum natura and by the ancient Greek philosopherEpicurus in his Letter to Menoeceus, in which he writes; Paraphrasing philosopher Paul Edwards, Keith Augustine and Yonatan I. Fishman note that "the greater the damage to the brain, the greater the corresponding damage to the mind. The natural extrapolation from this pattern is all too clear — obliterate brain functioning altogether, and mental functioning too will cease". Contemporary atheist scientists Steven Pinker and Sean Carroll assert that death is equivalent to eternal oblivion, as physical theories based on scientific materialism allow for no mechanism to continue consciousness after death.
Thomas W. Clark, founder of Center for Naturalism, wrote a paper titled "Death, Nothingness, and Subjectivity". He critiqued what he saw as a flawed description of eternal oblivion as a "plunge into darkness". When some imagine their deaths, they project themselves into a future self which experiences an eternal silent darkness. This is wrong, because without consciousness, there is no awareness of space and no basis for time. For Clark, in oblivion there is not even an absence of experience, as we can only speak of experience when a subjective self exists. According to neuroscientistGiulio Tononi, consciousness is "all we are and all we have: lose consciousness and, as far as you are concerned, your own self and the entire world dissolve into nothingness."