ON THE SUBJUNCTIVE TENSES
When it comes about subjunctives, the first meaningful problem that comes to my mind is the famous deflationist claim that the Tarkian sentence below:

English

[S] The sentence `the snow is white' is true iff the snow is white in a certain world.

merely involves a disquotation device, does not apply if the sentence is produced in a Romance language. Accordingly, there is an important and large semantic difference clearly captured by a tense distinction between the quoted and non-quoted statement:

Portuguese

[S'] A frase "a neve ? branca" ? verdadeira se e somente se a neve for branca num certo mundo. (Subjunctive Future for=will be)

[S"] A frase "a neve ? branca" ? verdadeira desde que a neve seja branca num certo mundo. (Subjunctive Present seja=that it be)

[S"'] **A frase "a neve ? branca" ? verdadeira se e somente se a neve ? branca num certo mundo. (Indicative Present ?=is)

(The * sign marks ungrammaticality.)

There are more issues involved beyond this one, as pointed out by many linguists. Here comes an interesting paper on the Subjunctive issue:

The Lazy (French)man's Approach to the Subjunctive

(Reference to Worlds, Presuppositions and Semantic Defaults in the Analysis of Mood: Some Preliminary Remarks)

by Philippe Schlenker

First draft, UCLA & IJN (last modified: June 10, 2004; new title, no other modifications for the moment).

Abstract

It has proven rather difficult to provide a unified semantics for the French subjunctive (the difficulty applies more generally to Romance, but we concentrate on French). In this preliminary note, we suggest that this is because the French subjunctive is a semantic default, to be used just in case the indicative would have triggered a presupposition failure. Thus the environments in which the subjunctive appears do not form a natural class, although they are the complement of a natural class. Once this is established, a large part of the question becomes: what is the semantic contribution of the indicative? Modifying minimally the analysis of Stalnaker 1975 (which was concerned with English), we suggest that the indicative triggers a presupposition on the value of a world term w, of the form w{CS}, indicating that the world denoted by w lies in the Context Set of individual x' at time t' in world w' (x', t', and w' may be left free -- if the context provides them with a salient value -- or they may be bound). This derives indirectly the intuition, found both in traditional grammar and in recent research (e.g. Farkas 2003), that the indicative marks an assertive act on somebody's part, though this person need not be the speaker. We also discuss an extension of this theory to the German Konjunktiv I, which we analyze in essence as a reportive indicative, in line with the intuitions though not with the implementation of Fabricius-Hansen & Saeb?? 2004. If correct, the theory we sketch makes it possible to analyze mood by analogy with person and tense as introducing a presupposition on the value of word-denoting terms, and in particular on world-denoting variables.

If you want to comment on this paper, you may also go to Kai von Fintel's blog.

PS:

I would like to hear from the German native speakers whether they agree or not to the following statements from Schlenker's paper:

There is a further piece to this puzzle. As noted in Schlenker 2003a and Fabricius-Hansen & Saebo
2004, the Konjunktiv I cannot be used when the thought or assertion is attributed to the speaker at the
time and in the world of utterance (the following is from Schlenker 2003a):

(63) a. *Ich glaube, da? Maria krank sei

I believe that Maria sick is-KONJ1

b. Ich glaubte, da? Maria krank sei

I believed that Maria sick is-KONJ1

`I believed that Maria was sick'

c. Peter glaubt, da? Maria krank sei

Peter believes that Maria sick is-KONJ1

`Peter believes that Maria is sick'

d. Peter glaubte, da? Maria krank sei

Peter believed that Maria sick is-KONJ1

`Peter believes that Maria is sick'

This suggests that the Konjunktiv 1 is -despite its name- an indicative, though with the special
requirement that the Context Set it refers to should not be that of the actual speaker at the time and in the
world of his utterance. We also obtain in this way the observation that the Konjunktiv I cannot occur in
conditionals, since the Context Set which is relevant for conditionals is always that of the speaker at the
time and in the world of utterance.

Do you agree with the indicative analysis of the Konjuctiv 1?