Ophiolite
Valued Senior Member
Context."I can assure you that flying saucers, given that they exist, are not constructed by any power on earth."
---President Harry S. Truman, 1950.
Truman was being challenged as to the possibility that UFOs were secret government craft.
No pay attention - if English is your first language you really should have understood this.
Given that they exist = if we assume that they exist = if for sake of argument we assume they exist
Truman was debunking the existence of flying saucers and implicitly questioning whether there was anything at all to be considered anyway.