Breakdown of Er muss das Fenster mit einem Pflasterstein eingeschlagen haben.
ein
a, an (eine)
er
he
haben
to have
müssen
to have to, must
Questions & Answers about Er muss das Fenster mit einem Pflasterstein eingeschlagen haben.
Why do we use the present tense muss here if the smashing happened in the past?
We are making a present-day assumption about a past event. To do this, German uses the present tense of the modal verb (muss) combined with a past infinitive construction at the end of the sentence (eingeschlagen haben). If you used the past tense of the modal (Er musste das Fenster einschlagen), it would change the meaning to an obligation: "He was forced to smash the window."
Why is it eingeschlagen haben and not haben eingeschlagen at the end of the sentence?
In a Perfekt Infinitive phrase (meaning "to have done" something), the auxiliary verb (haben or sein) always comes after the past participle. Since the modal verb muss pushes this entire infinitive construction to the end of the clause, haben takes the absolute final position.
How would the meaning change if we used dürfte instead of muss?
Er dürfte das Fenster eingeschlagen haben means "He probably smashed the window." While muss expresses near absolute certainty (around 90-95%), dürfte expresses a strong probability (around 75%), much like saying "I assume he did it" or "He likely did it."
What does the prefix ein- add to the verb schlagen here?