I would like to understand the difference between these two:

"It needs to have been deviated for 1 minute"
"It needs to be deviated for 1 minute"

Are both saying that the deviation needs to be occuring over time? I think that the past infinitive is just for that but on the other hand, wouldn't the other sentence mean the same?

  • 1
    It's not necessarily wrong, but this usage of transitive "to deviate [something]" is pretty unusual. Depending on the exact context, probably divert would be more suitable. – FumbleFingers Reinstate Monica Aug 14 '14 at 15:18
  • @Silkyss, is deviate in this sense some technical process, perhaps in Chemistry or Engineering? – Will Murphy Aug 14 '14 at 17:10
  • Yes, IT technical documentation. – Silkyss Aug 14 '14 at 17:19

Both of these expressions are ungrammatical. Deviate is an intransitive verb: it means to diverge from an appointed course or established value, not to cause something to diverge.

An intransitive verb cannot be cast in the passive voice. Consequently you must say:

It needs to have deviated for one minute. OR
It needs to deviate for one minute.

If these sentences define the circumstances under which some subsequent event is triggered, such as a correction or a warning message, there is no significant difference between them: both express the fact that action is taken after a one-minute deviation.

If this is not the case—for instance, if the deviation is actively desired in order to accomplish your purposes—then the distinction drawn by magistermurphy is operative: the sentence with the perfect construction looks to a point in time after the deviation, while the sentence with the simple construction looks to a point before the deviation.

  • THanks. But I think it can be cast in the passive voice like this: It needs to be deviated from the baseline ... Would that be correct? – Silkyss Aug 14 '14 at 15:28
  • @Silkyss No: only transitive verbs can be cast in the passive. You cannot deviate something, so something cannot be deviated. – StoneyB on hiatus Aug 14 '14 at 16:15
  • strange. The following sentence was written by a native speaker: .... has been deviating from the baseline long enough and activates the system. – Silkyss Aug 14 '14 at 16:29
  • @Silkyss That is not a passive construction, which is built with BE + past participle but a progressive construction, built with BE + present participle (-ing form). (Specifically, it is a present perfect progressive.) – StoneyB on hiatus Aug 14 '14 at 16:37
  • THank you very much. So even if the text is technical, I cannot say use "it needs to be deviated from ...", right – Silkyss Aug 14 '14 at 17:14

The sentences do not mean the same thing. "It needs to be deviated for 1 minute" means that this is the next step, that it should be deviated now.

"It needs to have been deviated for 1 minute," means that it should already have happened. It means the same thing as, "Before the next step happens, the one minute of deviation must already be done."

  • Are you sure "It needs to have been deviated" is correct, grammatically? – Manish Giri Aug 14 '14 at 14:25
  • Yes. See here under "perfect infinitive: passive." grammaring.com/the-forms-of-the-infinitive – Will Murphy Aug 14 '14 at 14:28
  • But deviate is intransitive and cannot be cast in the passive. – StoneyB on hiatus Aug 14 '14 at 16:46
  • That's true. I had assumed this was a technical use of deviated and that it could be used passively in that technical sense. If that is not the case, both expressions are ungrammatical, as @StoneyB said. – Will Murphy Aug 14 '14 at 17:01

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