They set up an experiment to test their new hypothesis. (COCA)

When reading the above sentence, how should we "parse" the infinitival clause?

  1. As an adjunct indicating the goal with adverbial function: They set up an experiment for the purpose of testing their new hypothesis.

  2. As a modifier in which the to-infinitival clause modifies/qualifies its previous noun phrase as is in relative clauses: They set up an experiment that is to test their new hypothesis.

  3. Both of the above.

  • 1
    You just answered it. for the purpose of = to isn't it? I dressed nice to look attractive = I dressed nice for the purpose of looking better. What's the confusion?
    – Maulik V
    May 19, 2014 at 3:56
  • 1
    The confusion is whether interpretation 1 or 2 is correct, or if both are possible (or equivalent). The OP hasn't answered their own question.
    – user230
    May 19, 2014 at 6:27

1 Answer 1


It's impossible to tell without further context, because the two are equally grammatical.

As rightly noted, the two options are not structurally equivalent, and they also emphasize different parts of the sentence. By using the clause to add additional description, 1 focuses on the verb and 2 on the object. Having the appropriate context might rule out one of the readings. Here are two expanded versions of the sentence in question:

  1. They, for the purpose of testing their new hypothesis, created an experiment.

  2. They created an experiment of the type which tests the new hypothesis.

"Why did they set up the experiment?" and "What kind of experiment did they set up?" clearly only accept one of the two responses. Giving the wrong parsing of the sentence in question during conversation would likely yield a confused look from the asker; though with some mental effort the desired information could be extracted.

Conversely, it may also be possible that both readings are appropriate. Consider:

What did the lab team prepare today?

They set up an experiment to test their new hypothesis.

Here, the meaning is essentially the lab team prepared an experiment, and as a result, the new hypothesis will get tested. The structural choice between they set up an experiment of the type that tests the new hypothesis and they set up the experiment for the purpose of testing the new hypothesis is incidental, as both convey roughly the same semantic meaning in this case.

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