Physicists are often asked why the image of an object, such as a chair, appears reversed left-to-right rather than, say, top-to-bottom when viewed in a mirror.
Topic
Why mirrors appear flipped left-to-right
Framework
Challenge a Position / Present a Debate / Explain Something Curious
Main Point
The front-to-back explanation of what mirrors do, unlike the field-of-sight explanation, is faulty because the 'behavior' of mirrors is dependent on an observer, which that explanation fails to capture.
Summary
P1 - The Standard Explanation (field-of-sight)
The passage begins by explaining how physicists answer the question of "why images appear reversed left-to-right in mirrors". Their explanation is called the field-of-sight explanation and holds that, It's not clear in realtime that the author endorses this explanation.
P2 - The Alternate Explanation (front-to-back)
We begin with a PIVOT (however), so this seems very important. Is this the author's preferred explanation? We find out that the author has at least some problems with it towards the end of the paragraph, when she points out that it's based on a false premise that it treats as though it's a real thing.
P3 - Explaining the Appeal / the Problem with the Alternate Explanation
The author begins by making some sympathetic concessions -- . - appeals because it's successful to a point - it seems natural to trust our mental constructs - but mirrors are an exception!
P4 - Continuing to explain the Appeal / the Problem
This paragraph also discusses why this front-to-back explanation can be appealing before discussing her ultimate problems with it. How are P3 and P4 different? P3 is more about why regular people would like it but should think twice about it. P4 is more about why scientists would like it but should think twice about it. - yes, it's nice that this explanation removes the observer from the phenomenon, as we aim to do in science. - However, we're trying to explain why mirrors appear as they do, which is nonsensical to speak of how they appear unless there's an observer perceiving them.
Commentary
I found this passage a tricky read, in terms of guessing where the author was ultimately landing. She never explicitly indicates that she likes the field-of-sight explanation, but since it does explain mirrors in relation to the observer, she presumably would be fine with it.
When you re-read the first paragraph and beginning of the 2nd thinking that she likes field-of-sight and doesn't like front-to-back, you might notice that the first paragraph is attributed to physicists, like the whole group, the mainstream, the standard.
The second paragraph is attributed to some physicists, which we might ultimately come to think of as the exceptions, the outliers, the rogue physicists. Our author apparently wants to explain why their thinking is whack
We could think of this passage as a Debate, since there are two different points of view on how to explain how mirrors appear (and author chooses Side A).
We could think of it as Challenge a Position, with the author challenging the front-too-back explanation.
Or we could think about it as Explain Something Curious, the curious thing being how mirrors seem to flip the left/right image of an object in the reflection. Paragraph 1 and 2 each give a separate Explanation, and the author discusses the appeal but the ultimate problems with the second Explanation.