Today I told someone who said that there is no objective truth the next thing: "For example, we, as humans, cannot know if God exists or he does not but we can know for sure that one of these two possibilities is true. So, you see, there is an objective truth, but not accessible from a human perspective". And his reply was: "There can be another state besides existence and nonexistence but we, from a human perspective, can only see these two".
When I studied at University an eminent Professor (since that time author of a book entitled " Causa sive ratio : la raison de la cause de Suarez à Leibniz " ) once asserted during a course on metaphysics the following paradox :
" he is a religious man who precisely does not believe God exists".
The "joke" refers to the precise meaning of the verb " existing" ( in medieval philosophy).
What "exists" is litteraly what stands out (of its causes). The verb "existing" only applies to finite beings, having causes ( different from themselves) , taken in the flux of becoming.
So according to medieval theologians it is both false (1) that God is not ( has no reality) '2) that God exists. God is ( is real) , without existing ( his mode of being is not existence). To believe that God exists is to believe that God is a finite being: that would be idolatry !
This view is called non-dualism. If you google you'll be snowed under.
Assertions of existence and non-existence embody positive metaphysical positions. For non-dualism all such positions would be wrong and demonstrably so.
One way into the topic would be to study Nagarjuna's doctrine of 'Two Truths'. He proves that nothing really exists. The word 'really' indicates it would be incorrect to state that nothing exists or that something exists, the truth being more subtle.
Likewise consider Heraclitus and his statement 'We exist and exist-not'. This is a statement of non-duality and a refusal to say we do or do not exist, the truth being more subtle.
Your friend is wrong to suppose that from a human perspective we can only see existence and non-existence but no third alternative. Most practioners of meditation see beyond this duality if they keep going. Indeed. the whole point is to see beyond dualism.
Yes. Possibilities. David Lewis in "On the Plurality of Worlds" argues that all possible worlds somehow actually exist though I don't think most contemporary philosophers buy into this idea. Lewis does allow for what he calls a kind of "ersatz" existence for possibilities (if you want to talk about possible worlds without making existential claims). But here's my personal take on the subject (based in part on quantum mechanics). In quantum mechanics subatomic particles, strictly speaking, exist only as a range of possible "states" which only "collapse" into a single, "existential" state when observed. So I would think this range of potential states would qualify as something other than either actual existence or nothingness. Depends, I guess, on what you mean by "existence". But to me it seems that realized possibilities (existence) are essentially different from unrealized possibilities (neither existence nor non-existence) and, of course non-existence.
Meinong's concept of 'subsistence' is relevant here. The following is a brief explication:
According to Meinong's ... theory, there are two modes of being, existence and subsistence. Concrete objects that have being exist, and abs- tract objects that have being subsist. Concrete objects that do not exist have no sort of being whatever, and abstract objects that do not subsist have no sort of being whatever. The Cheshire Cat does not exist, and, cats being concrete objects, there is no Cheshire Cat. The operation 'division by o' does not subsist (unlike the operation 'division by 2', which does subsist), and therefore although there is such a thing as division by 2, there is no such thing as division by o. Nevertheless, the phrases 'the Cheshire Cat' and 'division by o' have referents, and we can think about these referents and say true things about them, things like 'The Cheshire Cat has a tail' and 'Division by o plays a hidden role in several well known fallacious proofs'. These true things are true for this straightforward reason: each ascribes to an object a property the object has. The Cheshire Cat counts having a tail among its properties, and 'playing a hidden role in several well known fallacious proofs' is one of the properties of division by o. (A note on terminology: in this exposition of Meinong, I have, anachronistically, used the terms 'concrete' and 'abstract'. I am willing to defend the anachronism if anyone wants to go into the matter.) (Peter van Inwagen, 'McGinn on Existence', The Philosophical Quarterly (1950-), Vol. 58, No. 230, Special Issue: Existence and Identity (Jan., 2008), pp. 36-58: 38-9.)
There is the view of the possibilists. (Here I am not going to name any names. A lot of philosophers hold, or have held, this view, however. Take my word for it.) Possibilism has its roots in philosophical reflection on the standard Kripke-style semantics for quantified modal logic. Possibilism divides things, divides the things that are, into two exclusive classes: the things that actually exist, and the things that do not actually exist, that is, the things that might exist but do not. The possibilists' use of the word 'actual' to mark this distinction can be traced to the occurrence of this word in the phrase 'the actual world': actually existent things are the things that exist in the actual world, and merely possible things (things that might exist but do not) are the things that exist only in non-actual or merely possible worlds. But it is clear that whatever may have been the possibilists' reasons for using the word 'actually' in this context, the word is redundant, for things that do not actually exist are just things that do not exist, full stop - just as things that are not actually red are things that are not red, full stop. (Or I can put the point in this way: it is an easy logical step from 'x might exist & x does not exist' to 'x does not exist'. (Peter van Inwagen, 'McGinn on Existence', The Philosophical Quarterly (1950-), Vol. 58, No. 230, Special Issue: Existence and Identity (Jan., 2008), pp. 36-58: 40.)
So for possibilists there are things that exist, things that do not exist, and things that might exist - the last forming a category which is not that of the merely existent or of the merely non-existent.