This week’s tip? Beware of illogical comparisons. When you use “in contrast with,” “compared with/to,” “like,” or “unlike,” make sure that the items you are comparing fall into the same category.  Here’s an example of an illogical comparison:

In contrast to Figure 1, which shows the conventional process, no intermediate ion-pair is formed during the novel process shown in Figure 2.

In this sentence, the word order results in an illogical comparison between “Figure 1” and “intermediate ion-pair.” To revise, make sure that the “in contrast to” phrase is immediately followed by the second of the two items being compared:

In contrast to the conventional process (Fig. 1), the novel process shown in Fig. 2 does not involve formation of an intermediate ion-pair.

Here’s another example, in which “surface area” is illogically compared with “zeolites”:

Compared with the parent zeolites, the surface area of the modified zeolites decreased.

There are several ways to revise this sentence:

Compared with the parent zeolites, the modified zeolites showed decreased surface area.

The surface area of the modified zeolites was smaller than that of the parent zeolites.

The modified zeolites had less surface area than the parent zeolites.

Can you spot the illogical comparisons in the following sentences? (Suggested revisions are indicated in italics.)

(1) The absorbance intensities of the bands at 1200 and 980 cm–1 for the treated residue were compared with the untreated residue.

The absorbance intensities at 1200 and 980 cm–1 for the treated residue were compared with those for the untreated residue.

(2) In contrast to the Mycobacterium strains, PAH degradation by our isolates required the presence of an inducer.

In contrast to the Mycobacterium strains, our isolates required an inducer for PAH degradation.

(3) Unlike the glycopeptides isolated from the mutants, a simple mass spectrum was observed for the glycopeptides isolated from wild-type strain.

Unlike the glycopeptides isolated from the mutants, the glycopeptides isolated from the wild-type strain showed a simple mass spectrum.

(4) Unlike ethylene, hydrogenation of 1-butene proceeded at a moderate rate.

Unlike ethylene, 1-butene underwent hydrogenation at a moderate rate.

Unlike hydrogenation of ethylene, hydrogenation of 1-butene proceeded at a moderate rate.

Various usage books discuss such illogical comparisons and provide additional examples. See, for example, Bryan A. Garner, Garner’s Modern American Usage, 3rd ed. (Oxford: Oxford University Press, 2009), p. 440; Marjorie Skillin et al., Words into Type, 3rd ed.  (Englewood Cliffs, NJ: Prentice-Hall, 1974), pp. 368–369; and Edward D. Johnson, The Handbook of Good English (New York: Washington Square Press, 1991), pp. 13–14, 20, 363.

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