"das" vs "dies"

Question

From what I have seen on grammar specialized websites das and dies are not declined when they are used as subjects in combination with sein. Example: Dies sind Zeitungen.

Apart from this, are there any other instances where das/dies can't be declined?

For example when the object of the action is a masculine noun and we wish to replace it with das/dies:

Ich habe einen Hammer gefunden.

With das/dies:

=》Ich habe das/dies in der Garage gefunden.

or

=》Ich habe den/diesen in der Garage gefunden.

Are diesen/den in accordance with the grammar rules here? Do you think das/dies would fit better?

Edit: I would much apreciate some other examples of sentences in which the pronouns das and dies are not declined and don't act as subjects, if there are any.

Answer 1

The words das or dies are declined regularly. There are no rules that restrict their declension.

The subject of a sentence is almost always in the nominative case (exceptions are extremely rare). So when the words das/dies function as the subject of a sentence, they will take their nominative declension form. When they are used in other grammatical functions that have other cases, they will take other declension forms in the appropriate case.

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Being neutrum pronouns, the accusative form of dies/das is the same as the nominative form:

• Nominative/accusative: dies/das
• Genitive: dieses (rare)/dessen
• Dative: diesem/dem

Examples with dative:

Ich kann diesem/dem nicht zustimmen.

Von diesem/dem halte ich gar nichts.

Examples with genitive (note that a pronominal use of the genitive dieses would be extremely unlikely and confusing because it sounds the same as nominative dieses):

Dessen Einfluss nimmt zu.

Ich entsinne mich dessen.

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What happens with the case you have given as an example is that it does not use neutrum das or dies at all, but masculine der or dieser instead:

Ich habe diesen/den in der Garage gefunden.

This can be shown by transforming the sentence into the passive voice:

Dieser/der ist in der Garage gefunden worden.

With neutrum dies/das, the sentence would be as follows:

Ich habe dies/das in der Garage gefunden.

Answer 2

This question cannot be answered without an available context. If you went into your garage and found something surprising such as a pistol, for example, you would show the item to someone and say "ich habe das in der Garage gefunden!". In contrast, if someone asked you to look for a pistol in your garage, you would show the item and say "ich habe diese (feminine) gefunden" because the feminine word "Pistole" constitutes common background for speaker and hearer.

Answer 3

im a native german and here is my answer: Actually, most germans dont know the difference themselves, so the answer really is that you (when talking normally) almost never say "dies", but im not shure however, how much of a formal german you learn