If person #1 does not believe person #2 exists, can they still be in relationship?

Introduction

The question most directly relates to the problem of divine hiddenness: if a loving God exists, then wouldn't that God make sure no one is an atheist or agnostic, so that everyone is at least able to be in relationship with God, just by trying?

One response says that, plausibly, belief in God is not required for relationship with God. But is that plausible? As counterintuitive as it might seem at first, can two people be in a relationship when one party doesn't even believe the other exists?

“Yes, after all…

... not required in the possible-hallucination case

One can enter into a relationship with what plausibly seems to be a hallucination or imaginary friend, yet is actually not a hallucination.¹ This is relevant because in such a case, one does not have a belief that another person exists.

• Andrew Cullison: “Suppose Bob recently discovers that he has been (for several years) hallucinating people and from his perspective developing very sophisticated, complex relationships. After Bob spent several months in the hospital, the doctors have determined that he has been cured. They are confident that he will no longer hallucinate. Julie is one of the doctors. Bob is skeptical that Julie is real. He even says on several occasions, 'I really don’t believe you exist.' However, Bob thinks to himself, 'Julie (if real) would be the most amazing person I have ever met, and I am cofident that we could have a long-lasting relationship. I could never forgive myself if I didn’t give her exactly the kindness she deserves (if I discovered she were real), so I’ll continue this relationship.'” [“Two Solutions to the Problem of Divine Hiddenness” American Philosophical Quarterly 47:2 (2010): 120.]

...not required in the comatose-person case

You could form a relationship with someone while being unsure of whether they are conscious, while they in fact are conscious.¹ This is relevant because if you could form a relationship with someone like that, then you can form a relationship with someone while not knowing whether they exist.

For example, imagine I were comotose. You come to visit and share details of your life and feelings with me, perhaps your search for God. In that case, and especially if you are talking to me about what they are appreciating and learning from my website, we would be in a relationship. This relationship would exist even if I were not talking back, and even if you weren't sure I was consciously present.

...not required in the A.I. chatroom case

One can enter into a relationship with what plausibly seems to be an A.I. or simulated person, one which actually is a real person.¹ This is relevant because in such a case, one does not have a belief that another person exists.

• Andrew Cullison: “Bob is lonely and begins a chat-room relationship with Julie. Bob and Julie are both grieving the loss of a loved one. Julie offers words of encouragement that no one has been able to offer Bob. Bob does the same for Julie. Then Bob’s friend Steve provides Bob with an overwhelming amount of evidence that chatrooms have very sophisticated Turing machine programs that can perfectly replicate close, personal conversation with other humans. Bob is nervous. It is highly likely that Julie is a fake. He stops believing that Julie exists. He even tells Julie that he doesn’t believe she exists. However, he holds out strong hope that Julie exists. He says, 'you may not be real, but there is some very slim possibility that you are—that’s enough for me to think this is worth continuing.' Eventually, they meet. They marry. Someone asks them 'When did your personal relationship begin?' Bob says, 'Back when I didn’t even believe Julie existed.'” [“Two Solutions to the Problem of Divine Hiddenness” American Philosophical Quarterly 47:2 (2010): 120. ]

...not required in the tapping prisoners case

Prisoners in solitary confinement making tapping noises to each other can be in a relationship, while not being sure whether the other exists.¹

• Trent Dougherty & Ted Poston (Philosophy profs at Baylor & South Alabama): “Suppose that Jones—an unfortunate fellow—is locked in solitary confinement in a dark prison cell. Jones hears faint taps coming from the other side of his prison wall. The taps resemble the presence of another person willing to communicate, but it is not certain that there is another person in the other cell. Yet, Jones begins to tap back. Suppose this activity continues over a long period, and Jones can—with some effort—make sense of the taps as another person attempting to communicate with him. Suppose Jones’s credence (his degree of belief, rational confidence, or what have you) on the claim 'there is another person in the cell beside me' is .5. He seems to be discerning messages, but he realizes that it could just be in his head since the signs are ambiguous. Yet, given that the two persons are tapping back and forth to each other, it seems that they are in a personal relationship, one which in time could take on great significance (again, this latter part is of great importance). The interaction could be so meaningful and hope-inducing that it keeps Jones from going insane or perhaps even keeps him from dying or killing himself. Suppose also that in fact the tapping is coming from Smith who, many years later, meets up with Jones and they discover what was going on. We submit that this part of their relationship will take on newfound significance in their new relationship, something to look back on and cherish, and a surprisingly good foundation for deepening their relationship now that Jones’s credence has been raised to moral certainty by actually meeting Smith.” [“Divine Hiddenness and the Nature of Belief” Religious Studies 43 (Cambridge, 2007): 190-191.]

..not required in the unknown benefactor case

One can enter into relationship with an unknown benefactor.¹ This is relevant because the relationship with a person does not require belief that a know person gave you the gift.

Trent Dougherty & Ted Poston: “Suppose in a moment of need some extra money shows up in your bank account. You ask the bank if it is a mistake and they say that an anonymous donor has wired you the money. You think to yourself, “Thank you, whoever you are.” Now in this case you lack de dicto belief, but—especially if the other person can see your reaction (e.g., they are standing nearby)—it is fair to say that the two of you have a meaningful relationship.
Now we tell the story for low degree of belief. Again in a moment of need some extra money shows up in your account. The bank tells the same story as before, but this time you suspect who has done it, though you have around .5 confidence (perhaps less) that you are right. So you have a de dicto belief to the effect of “so-and-so did it” but you have a low degree of confidence in this proposition (e.g., slightly greater than .5). Just in case, you send an anonymous thank you note to the individual. That way, if it is him, he will know who sent it and if it is not, you will not have to explain yourself. Now suppose you are right; it is in fact whom you suspected. It is fair to say you have a meaningful relationship. You have successfully expressed your gratitude to the individual and they have received it.
Now combine the two distinctions and consider a case in which you have neither a high degree of confidence nor de dicto belief. Again in a moment of need some extra money shows up in your account. You do not know if this is a mistake or if someone has given you this money. For whatever reason, it just doesn’t occur to you to ask the bank to figure it out. You suspect, though, that someone has in fact transferred this money to you and you think to yourself, “Thank you, whoever you are.” Now in this case you have neither de dicto belief nor a very high degree of belief, but—especially if the other person can read your mind—it is fair to say that the two of you have a meaningful relationship. And as we noted above, this relationship can take on a new level of retrospective significance if in the future you meet the person. We refer to this as the “unknown benefactor case.” [“Divine Hiddenness and the nature of belief” Religious Studies 43 (Cambridge, 2007): 192-193.]