18 Biological Immortality showed? Can’t be stopped, definitely inevitable, so no point worrying about it.” And with further questioning about immortality, they will reply as follows. “Immortality, you ask? Well, that’s a Greek myth, isn’t it?  Nothing  to  do  with  biology.  Everything  dies,  so immortality can’t be a real thing, no way. It’s a joke played on us by religions.” So saying, Professor Corngold will shake his head with relief, grateful that there was at least one question he could answer without having to refer to a textbook. AN APPROPRIATE TERMINOLOGY FOR AGING AND IMMORTALITY Yet, very few of the superstitions that biologists and medi- cal doctors believe about aging, immortality, and death are true. To explain this, some refinements of terminology are required: The most objective definition of aging is that which occurs when  rates  of  survival  or  reproduction  inexorably  decline, even when organisms are kept in excellent environments, in which contagious disease has been virtually eliminated, with abundant  food  and  no  prospect  of  being  eaten.  [1]  Some people like definitions of aging that include falling perfor- mance,  increasing  pigment  levels,  reduced  cell  replication, and so on indefinitely. But these definitions depend on the particulars of the biology of the organism. By contrast, all organisms have rates of survival and reproduction and when survival probabilities fall to low enough values, organisms die. It is also important to exclude all reasonable external agents