When can verbs be omitted in German sentences?

Question

I see in some of Paul Tillich's texts that he omits certain verbs, usually the verb sein or to be. However, when I searched on Google, I was unable to find any entries on this feature of German. What are the rules governing the omission of verbs from German sentences? What other verbs can you leave out of a sentence?

Der Fortschritt der wissenschaftlichen Erfahrung entscheidet. Er hat entschieden, dass die Erde ein schwebender Körper, keine schwimmende Platte, dass die fünf Bücher Mose aus verschiedenen Quellen, nicht von Mose stammen.

There you can see that he omits the "to be" from the dass clauses. Does anyone know when one can do this? I saw it in a Youtube video, where the video creator said that you can shorten sentences sometimes by leaving out the verb. I wasn't sure if there was more to it than that.

Answer 1

It is indeed possible to shorten sentences this way, but the example you presented is just plain wrong. You can shorten sentences if they have parts in common by omitting the part they have in common, for instance:

Er hat entscheiden, dass die Erde ein schwebender Koerper [ist], [dass die Erde] keine schwimmende Platte ist.

Here, "daß die Erde" is ommitted in the second, the "ist" in the first sentence. But the shortened parts have to be common to allow for that. This is not the case here:

... daß die Erde ein schwebender Körper ist
--- daß die fünf [...] nicht von Moses stammen.

Having said this: there is indeed a poetic device which allows for exactly that: leaving out the Modalverb at the end:

Und rette mich, die du vom Tod errettet [hast],
auch von dem Leben hier, dem zweiten Tode.
_{Goethe, Iphigenie auf Tauris}

Here is another example:

Das an ihr hängt, dem Busen nah,
Und ihre Rosenwangen lecket
Und das oft viele Reize sah,
Die meinem Späherblick verstecket [sind].
_{Novalis, An Laurens Eichhörnchen}

But the text you quoted is hardly a poetic one and hence not eligible for this exemption.

Answer 2

Leaving out haben or sein at the end of a clause had been common practice in the old times. That style died out in the late 19th century. Nowadays no one would write like that other than for the purpose of sounding old-fashioned, or for matching a rhyme scheme in a poem.

In everyday texts, you can do it as an ellipsis, meaning, you can leave out all haben or sein or whatever else but the last one. But that's not the case here.