Only engineering is capable of analyzing the nature of a machine in terms of the successful working of the whole; physics and chemistry determine the material conditions necessary for this success, but cannot express the notion of purpose.
Conclusion
Only physiology can analyze whether the organs of an organism are functioning healthily.
Evidence
Physics and chemistry can't do it, because they can't measure whether a human body is operating "as it should". Physics and chemistry can't analyze whether a machine is successfully working as a whole, because they don't know what it means for the machine to be operating "as it should". Only engineering has language of purpose, of what successful functioning would mean / would look like.
(In other words, physics and chemistry can define the nature of things as they are, but they don't have any language to define whether things are successfully working at their purpose, only engineering or physiology can do that).
Evaluate
Yikes. This is an all-timer in terms of hard paragraphs to read.
In a boring formal sense, any time an author argues like this, Only Peter can do thing X. Because Joe and Reggie don't know how to do Y.
the author would be assuming . the author would also be assuming
So this argument is assuming .
and it would be assuming
Because of the word "Similarly", we know that the author is trying to Complete an Analogy, so we want to think about any of the parallels the author is assuming.
Goal
Look for an answer saying , an answer saying , or an answer that feels like it's supplying some idea the author assumed was parallel in both halves of the analogy.