Identity, as expressed by the symbol '=' or by Peirce's line of identity, is fundamental for mathematics, logic, and theories of ontology. But the criteria for determining whether two occurrences of similar things may be considered "identical" depend on the relevant context. A baby and an adult with the same name and DNA may be identical in a legal sense, but not in any practical sense. New research raises even more questions: "As a human evolutionary biologist, Ive reached the point where Im not totally sure what a human is -- where our biology ends and the environment begins." -- Rachel Carmody Source: https://news.harvard.edu/gazette/story/2019/10/study-finds-gut-microbes-adapt-quickly-to-changes-in-food-preparation In any human body, the cells with human DNA are outnumbered 10 to 1 by the microbes. With every breath, people gain and lose an immense number of molecules. During the same time period, they gain and lose many human cells. They are also gaining and losing orders of magnitude more microbial cells. And these microbes have a profound effect on human digestion, health, and mood. Without those microbes, we could not survive outside an artificially constructed sterile bubble. Should the microbes be considered part of the body or part of the environment? John
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