Arguments against existence of God.

[Angrboda]

You don't have to go searching the cosmos for a unicorn when you can demonstrate the nature of the unicorn in your room.  We know, for example, that the unicorn myth arose in the indus...much derived by glyphs in profile, and entered the western mind through the greeks not as myth or magic but as a sort of compendium of the wonderful animals living in the mysterious east.  They, in effect, took these stories and the glyphs at their word and appearance.  In doing so they also considered a number of creatures both extinct and extant interchangeably with this horned horse.  Because of the presence of this creature in the stories and records of antiquity, and it's usefulness as a thematic element in religious art, the latter stories concocted by europeans are completely outside the remit of any description of an actual animal...and whatever animal or animals the greeks may have been referring to with their own secondhand stories have absolutely nothing to do with the unicorn that does exist, in your room, in your mind.

This is why it's both pointless to go looking for a unicorn out on the heath...and why you don't need to travel to every heath to rule out the presence of a unicorn.  

More broadly, as a principle...we don't need to know everything, to know something.  The idea that there is a requirement of full knowledge in some general sense for specific knowledge is both absurd, and self defeating.  Consider this...you don't know everything, you haven't traveled to every heath, so how could you know that you have to travel to every heath in order to rule out the presence of x on a given heath.  You don't, you can't, and absent such full knowledge -every single one- of your own knowledge statements are thus..not knowledge.  You don't have full knowledge, so how could you rule out the proposition that your name isn't really your name?

We don't know that. What we know is that you stated it was true, so we would need to confirm where you got said information and how you went from point A (the question of unicorns) to B (They were and always have been a myth).  In other words, the source(s) need validation or the information is little more than someone's take on how events played out in the past.  Some swear Bigfoot is a myth and some spend their entire life trying to track him down.  Who's right? I dunno, and I'm good with that until someone shows me a high resolution photo that hasn't been photoshopped.  Until then, it's fine just to continue to say, "I dunno."

You're ignoring his point that you've eliminated the grounds for believing we know anything, thus leaving us with no rational way to decide what we should do as individuals and society. That's a problem you simply aren't grappling with by saying, "I dunno," to unicorns, because saying, "I dunno," to unicorns for the reasons you gave means saying, "I dunno," to everything, leaving us paralyzed and unable to act any way except irrationally. Is that a good thing?