It is impossibly incoherent to argue that you do not exist or are not instantiated in reality. In order to argue that you do not exist, you would need to exist. Ergo you must exist. It is thus self evident, irreducible and a claim to absolute (and not relational) knowledge about yourself and reality.
"I still say a church steeple with a lightning rod on top shows a lack of confidence"...Doug McLeod.