Besides having potential medical and biosafety applications, as well as challenging the foundations of biological engineering, xenobiology can also shed light on the epistemological and metaphysical questions that puzzle philosophers of science. This paper reviews this philosophical aspect of xenobiology, focusing on the possible multiple realizability of life. According to this hypothesis, what ultimately matters in understanding life is its function, not its particular building blocks. This is because there should, in theory, be many different ways to build the same function. The possibility of multiple realizability was originally raised in the context of AI's hypothesized capacity to realize mental functions. Because we still do not have any incontrovertible examples of digital minds, not to mention alien life of foreign biochemistry, the best way to test this philosophical idea is to examine the recent results and practices of synthetic biology and xenobiology.
Keywords: bioorganic chemistry; multiple realizability; philosophy of science; synthetic biology; xenobiology.
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