Quote
"A toy which people cry for, And on their knees apply for, Dispute, contend and lie for, And if allowed Would be right proud Eternally to die for."
"Most men live in order to make a living; when they have that, they live in order to make a good living; when they have that, they die. … This comment can be developed into a demonstration of human immortality. This demonstration could be stated as follows: It is the destiny of every human being to make a good living. If he dies before he does that, he has not fulfilled his destiny. … But if he makes a good living, then he has achieved his destiny, but the destiny of making a good living cannot be that he is supposed to die, but, on the contrary, that he is supposed to live well on his good living—ergo, man is immortal."

Immortality is the concept of eternal life and permanent resistance to death from natural causes. Some species possess "biological immortality" due to an apparent lack of the Hayflick limit.
"A toy which people cry for, And on their knees apply for, Dispute, contend and lie for, And if allowed Would be right proud Eternally to die for."
"Soren Kierkegaard, Christian Discourses 1848 Hong 1997 p. 205"
"If what I assume is true, it is still excellent to be convinced of it, but if there is nothing after death, I will at least during the time before my death be less burdensome to my companions because of complaints, and furthermore this folly of mine will not last long—for that would indeed be an evil—but in a short time will vanish."
"It And her immortal part with angels lives."
"I long to believe in immortality. I shall never be able to bid you an entire farewell. If I am destined to be happy with you here — how short is the longest life. I wish to believe in immortality — I wish to live with you forever."
"For I never have seen, and never shall see, that the cessation of the evidence of existence is necessarily evidence of the cessation of existence."