# (GRE) Parallel Structures

The following is a sample question taken from the revised version of the ETS-administered Graduate Record Examination (GRE). I normally try hard to understand the logic behind selecting the choices offered by the answer key and often, after a few minutes, I come through. Here, however, I seem to be grappling with the choice and the explanation provided for the last blank; I fail to understand why "symmetry" is indicated as the correct answer. Can someone please explain the reason for that answer?

Sample Question:

It cannot be denied that without creative reasoning it would not have been possible to (i)__ of classical physics. Yet classical physics has no contribution to make to the understanding of (ii)___. This kind of (iii)__ is surprisingly common in logic as well as in life.

Blank (i)
A. dispute the value
B. lay the foundations
C. understand the basics

Blank (ii)
D. creative reasoning
E. other sciences
F. the arts

Blank (iii)
G. circular reasoning
H. inflexibility
I. symmetry

Explanation:
The word ‘yet’ is the main clue. It indicates an opposite. Start with the first blank and eliminate choice A. You can also get rid of choice C since you can understand the basics of physics without creative reasoning. Now to form the opposite we can choose D for the second blank. Now we paraphrase what we have: creative reasoning was needed to get classical physics started, but classical physics can’t help us understand creative reasoning. Then we can select the final option. The statements we have so far are parallel constructions (a sort of symmetry) and are not inflexible.

• Since it is neither G nor H, it must be I and is explained by The statements we have so far are parallel constructions (a sort of symmetry) and are not inflexible - what is your issue? Commented Oct 21, 2013 at 5:45
• I've got an issue with it. I cannot use the term 'parallel constructions' here. 'R maps to P, but P does not map to R' is not a symmetric relation. Commented Oct 21, 2013 at 11:42
• I would say asymmetry or lack of symmetry. Terrible question.
– user24964
Commented Oct 21, 2013 at 13:09
• Thank you all for taking the time. @mplungjan my issue is that much like others I detect a lack of symmetry here. Commented Oct 21, 2013 at 14:00

The full statement would read as such with the word in question emphasized:

It cannot be denied that without creative reasoning it would not have been possible to lay the foundations of classical physics. Yet classical physics has no contribution to make to the understanding of creative reasoning. This kind of symmetry is surprisingly common in logic as well as in life.

One definition of symmetry reads as such:

symmetry — the proper or due proportion of the parts of a body or whole to one another with regard to size and form; excellence of proportion.

The GRE question is really stretching the definition of symmetry, here, but isn't technically wrong. Their particular note on the word is highlighting the construction of the comparison and not the actual relationship between the subjects:

The statements we have so far are parallel constructions (a sort of symmetry) and are not inflexible.

Under their usage of symmetry, here is a more simplistic example: