But the thing is we CAN put the mechanical parts back together and have life that is completely indistinguishable from life that wasn’t taken apart and put back together.
Life as a physical phenomenon has no mystical component.
The physical mechanisms of life are both necessary and SUFFICIENT for there to be life.
Or as Athel Cornish-Bowden put it in Perspectives in Biology and Medicine (2006)
If we ask similar questions about metabolism, for example why glucose 6-phosphate is produced by most organisms in glycolysis (catalyzed by the enzyme hexokinase mentioned earlier), then initially the argument runs in parallel to that for machines. If the answer is that glucose 6-phosphate is produced because glucose and ATP are available then that is the material cause; if we answer that it is produced as a result of the action of the enzyme hexokinase, then that is the efficient cause. So far so good, but when we ask where the hexokinase comes from there is no final cause: it certainly does not come from outside the organism, so it must be produced from within. We can trace back material and efficient causes for that, but we never reach a final cause. This is what it means to say that organisms are closed to efficient causation. In admitting it to be true, however, we are stepping outside everything that we know about machines, and everything we can derive from classical philosophy.
We are still far from full and satisfying answers to the questions that Rosen asks about what makes a living organism alive. In general terms his view of the essential difference between a machine and an organism was foreshadowed by John Locke more than three centuries ago, but his detailed analysis is mathematically very demanding. It has been followed up by few other authors, and asserting that the organization is circular is not the same as the same as explaining exactly how the circularity is achieved. The essential point is to recognize that there is a real problem: as he said, the questions are real, and will not go away by virtue of not being addressedso it is not sufficient to say that we do not like Rosens answer. If we regard it as unsatisfactory or just wrong we need to propose an alternative; we cannot pretend that there is no question to be answered. In summary, the classical reductionist approach to science can be understood as a way of understanding the functioning of a whole system in terms of the properties of its parts, but now we must learn to understand the parts in terms of the whole (Cornish-Bowden et al., 2004). To make Rosens ideas more easily intelligible to biologists they will need to be put in the context of current knowledge of biology, and the limits within which his interpretation of the circular organization of living organisms can apply need to be specied (Letelier et al., 2006).