He saw it coming - Er hat es kommen sehen. I understand it's not 'gesehen' because sehen is treated like a modal verb. However, if I were to say "he must have seen it coming" by adding 'er muss', it becomes "Er muss es kommen gesehen haben", instead of just kommen sehen haben. Why does the 'sehen' gain a 'ge-' in this case?

1 Answer 1


With "sehen", the Ersatzinfinitiv is optional. Your first sentence could simply look like

Er hat es kommen gesehen.

Which would be just about as correct and idiomatic as your example. "sehen" doesn't necessarily have to be considered a modal verb here.

Your second example, without the "kommen" looks like

Er muss es gesehen haben

(Remember Ersatzinfinitiv is optional with sehen)


er muss es kommen sehen haben

is just as correct and idiomatic as your example

er muss es kommen gesehen haben

lots of infinitives in a row, however is a complex thing that most native speakers' "Sprachgefühl" wants to avoid, so it remembers "ah, this was optional" and evades it.

Let's use an example where the Ersatzinfinitiv is not optional (because we're using a "true" modal verb). Assume you want to say

We will have had to accept our fate [Futur II]

this translates to

wir werden unser Schicksal haben hinnehmen müssen

No way to avoid the four infinitives in one sentence here.

  • Thank you for the very clear explanation! No grammar rules seem to have been broken then (no new exceptions to learn yay)
    – Jan Lynn
    Oct 6, 2020 at 20:04
  • Note that the construction "Er hat es kommen sehen müssen" is also possible, though with different meaning Oct 6, 2020 at 21:59
  • 1
    Werden is not an infinitive here, but 3rd person plural of werden. It does look like the infinitive though. Oct 7, 2020 at 10:04
  • @infinitezero Right. But well, I'll add another one, if you like ;) Insert between "hinnehmen" and "müssen": können
    – tofro
    Oct 7, 2020 at 10:06
  • @tofro we had another question about that, somewhere on this site :D Oct 7, 2020 at 10:07

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