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"Despite the enormous fund of information that [biologists] have provided," wrote Carl Sagan in 1970, "it is a remarkable fact that...there is no generally accepted definition of life." This book provides a gripping, (very) brief tour of the present "enormous fund of information" we now have on living functions:
1) Replication (the discovery of DNA in 1954; the breaking of the nucleotide/amino-acid Genetic Code in the 1960s--on through the Recombinant DNA revolution of the 1970s through "synthetic" viruses composed from genetic scratch in the 1980s),
2) Metabolism (the Krebs cycle; the universal role of ATP),
3) Evolution (the Modern Synthesis uniting genetics and natural selection)
Regis also describes attempts in this century to devise novel lifelike systems in the form of artificial "protocells" and chemical "chells"
Despite this veritable avalanche of information of how living systems work, it remains a baffling fact that the simple question, "What is life?" remains as disputed as ever. One begins to wonder whether this question might be an empty philosopher's quixotic quest. In this spirit, there might be something to be said for Edouard Machery's dilemma-diagnosis in his essay (discussed by Regis), "Why I Stopped Worrying About the Definition of Life...and Why You Should as Well" (2006): "the project of defining life is either impossible or pointless," he writes, since either 'life' refers to "a traditional and ill-defined 'folk notion'" or else the definition of 'life' is to be fixed by "a precise, scientific theoretical concept." If the former, then defining 'life' slides into Socratic silliness; but, if the latter, then *every* scientific sub-discipline will have its own 'fixed' definition...and there's nothing to be said beyond that (pp. 158-159).
I can't help but think that anyone who gives Regis's primer a read will soon be inspired to follow up by exploring many of the scientific vistas Regis points out.
