the subjunctive in the adjective clause

[Nfqufktc]

¡Hola!

I would appreciate it if you could comment on my line of reasoning with regards to what makes sentences 1 and 2 exempt from the need to be complemented with the subjunctive.

The grammar books only said that it was a case of the verb of wanting / needing vs. the verb of having and they did not elaborate any further.

1. Una chica compró [FOCUSED] sombra para los ojos que le daba [FOCUSED] un aspecto vampiresco.

A girl bought an eye shadow that made her look like a vampire / gave her a vampiresque appearance.

2. Tenemos [FOCUSED] una computadora que funciona [FOCUSED].

We have a computer that works.

The antecedent is computadora, an electronic machine (one of the many) = NOT A TYPE

3. No había [FOCUSED] ningún lago allí que no fuera [DEFOCUSED] contaminado.

There was not a single / one lake there that was not polluted.

The antecedent is lago, but it is one that the speaker asserts did not exist at some time in the past.

4. Necesitamos [FOCUSED] una computadora que funcione [DEFOCUSED].

We need a computer that works.

The antecedent is computadora, as a type of computer, not a specific machine.

5. ¿Prefieres [FOCUSED] una novela en que el héroe siempre se case con [DEFOCUSED] la heroína?

Do you prefer novels in which / where the hero always marries the heroine?

The antecedent is novela, one of a class, not a specific title.

I venture to suggest the folllowing explanation:

Necesitar and preferir can be broadly grouped as emotive verbs. If it is so, it is to express his emotion that the speaker must use one of the four subjunctive forms (which are devoid of factual meaning), according to the temporal logic of the verb system, to complement his sentence.

Tener, on the other hand, is, for lack of a better term, a bipolar / black and white verb (so is comprar). One either has a computer or does not. Its semantics precludes any vacilation with emotions and, as such, it is freed from the need to be complemented with the subjunctive.

To refer to the definition for applying the subjunctive in an adjective clause:

The subjunctive is used in a subordinated adjective clause when that clause modifies an INDEFINITE, VAGUE, or NON-EXISTENT (UNREAL) antecedent.

So, in the sentence Tenemos una computadora que funciona

Una computadora is an UNIDENTIFIED example of the existing computers that we may claim to be ours / have borrowed / may have given away, etc. It is neither INDEFINITE, nor VAGUE, or nor NONEXISTENT. It is real and tangible.

I am looking forward to having your clarifications and corrections.

Thank you.

[aleCcowaN]

I'm going to reply in several posts because it's a long topic.

First, you should replace FOCUSED with NO NEED TO DEFOCUSE and immeadiately stop using it, because things that happen or exist in reality or within the mental frame of an individual or group don't need focus: they are the bulk of what verbs express and Spanish indicative manages that quite well.

The FOCUSED/DEFOCUSED pair is just an artifact to help explain something that operates within the mental space of native speakers and is difficult to put in words, as it happens while Mentalese (the inner non-verbal language every one of us uses to think) is composed (unparsed) into proper Spanish.

Una chica compró [fact verified in the realm of reality] sombra para los ojos que le daba [personal opinion or an opinion reputed as general, so taken as an objective one, either of which we are "hereby" informing to belong to the realm of reality] un aspecto vampiresco

Una chica compró ["FOCUSED"] sombra para los ojos que le diera ["DEFOCUSED"] un aspecto vampiresco

with "FOCUSED" meaning the same as in the previous example and "DEFOCUSED" meaning it was the personal and subjective preference of the said girl and what she was especifically looking for.

This latter sentence sounds a little bit odd although its meaning is clear. It'd better have been

Una chica fue a comprar sombra para los ojos que le diera un aspecto vampiresco

that was her intention from the very beginning, but, did she find one?

On the other hand

Una chica compró sombra para los ojos que le daba un aspecto vampiresco

doesn't inform if that was the girl's intention. Maybe she believed she chose a make-up that suited her beautifully and end up Halloween-ready. I'm sure Tammy Faye thought her make-up was done consistently tastefully.

We'd have to add or subtract elements to these sentences to make them precise. It doesn't matter because subjunctive doesn't contribute to it.

The important thing is

Una chica compró sombra para los ojos que le daba un aspecto vampiresco

and

Una chica fue a comprar una sombra para los ojos que le diera un aspecto vampiresco

reveal that from the Mentalese stage the intention of our speech was fully set, and then the proper grammar elements were chosen in the composing (unparsing) process.

[Nfqufktc]

Thank you, aleCcowaN. I am looking forward to hearing your other thoughts.