My friend tried to claim that I could ONLY use fears named via Fear of the Unknown in that same game, claiming that I could not use a fear he’d stated in yesterday’s game with Fear of the Unknown, nor could I use a fear that I know he’s had his whole life (I’ve known him for a long time!)

A: Unfortunately your friend was taking too narrow of a view here. You are correct.

When playing Dream Thief, you are free to name or simply try to guess ANY fear that another player may have. If nothing has been admitted within the players’ memory (“But you just said yesterday that you were afraid of clowns!”) the target player is free to try to deny the claim*, but longstanding knowledge of a friend’s fears are just as valid as any explicitly stated during the course of the game, either the present game, or yesterday’s, or last month’s.

*If the target player wishes to dispute this, the onus is on them to justify it, however, it is quite possible to give plausible justifications for a lack of fear of something. For example:

SHARKS
Really? You’re not afraid of being eaten by a shark?
No, since I don’t expect to be swimming in shark infested waters, I do not consider this a general global fear – I don’t walk around every day in fear of being eaten by a shark.

BEING KILLED IN A CAR ACCIDENT
Really? You’re not afraid of being hit by a car?
I don’t even walk around in fear of being hit by a car. Of course, that would be a crappy thing to happen, so naturally, I use normal caution to avoid this terrible outcome, but that doesn’t mean I have a fear of that thing specifically. Since I avoid it fairly easily, I have no need to fear it.

DEATH
Really? You’re not afraid of dying?
Okay, fine. Death scares me. I’m sure if I were on the brink of dying or actually in a situation where I might die (having just been hit by a car and bleeding out on the side of the road, or swimming and seeing a giant shark fin nearby) I’d be feeling fear.

alternatively:
DEATH
Really? You’re not afraid of dying?
No, I really believe I’m at peace with the idea of my eventual non-existence.
or
No, I believe that I’ve lived a full life, and I’ve been a good person, and I’ll see my loved ones in heaven.

Of course, you can’t just keep guessing like this. These are just a few examples of possible responses. Yes, they have to justify their denial, and having received justification, you could debate it (civilly!) but you can’t take an alternate guess. If you guessed wrong, you just move on.

Seriously, this shouldn’t have to cause strife among friends.