Not necessary, because the argument just requires that the relationship between certain concepts in the machine analogy is similar to the relationship between certain concepts in the case of an organism. Specifically, the assumption is that the relationship between a machine’s purpose and the nature of machine is similar to the relationship between the operational principles of organs and the nature of an organism. But this doesn’t require that a human organism “function” like a machine. For example, the way we run, jump, speak, or think, doesn’t have to be similar to how a machine would move or make sounds or generate ideas.

Not necessary, because the core of the author’s reasoning involves what physics and chemistry are unable to do. They can’t analyze the operational principles of a body’s healthy functioning, just as they can’t determine the material conditions that make a machine successful. The argument doesn’t depend on what physics/chemistry CAN do; the focus is on their limits.

Necessary, because if it were not true — if the notion of purpose as it relates to machinery does NOT have an analog in organisms — then the machine analogy provides no support to a conclusion about analyzing organisms. The author pointed out that physics/chemistry couldn’t analyze the purpose of a machine as a reason that those disciplines couldn’t analyze what makes a machine successful. But if “purpose” doesn’t have a similar concept in organisms, then we have no reason to think physics/chemistry couldn’t explain organs’ roles in a healthy body.

Not necessary, because even if physiology has some overlap with physics/chemistry, it can still be a different discipline that can analyze things physics/chemistry cannot.

Not necessary, because even if biological processes can be reduced to mechanical or chemical processes, the author’s point is that there’s something else that we need to take into account in order to analyze the nature of an organism — we need to take into account operational principles. As long as these operational principles cannot be entirely explained by physics/chemistry, the author’s reasoning still works.