There is no such thing as a true agnostic. The overwhelming majority of people who identify themselves as 'agnostic' are in fact 'agnostic atheists', which most atheists are, as well.
An absolute agnostic is a person who, after reviewing the physical evidence and philosophical arguments for and against the existence of gods comes to the conclusion that it is equally probable that deities do exist as it is that they do not.
Even a person who has never heard of the existence of any religion cannot be categorized in this position because in order to arrive at it one must first be aware of the concept of god and then consider it.
Therefore, in practical reality, an absolute agnostic most likely doesn't exist.
People who claim to be an out-and-out agnostic are either exceedingly ignorant of the English language or they simply claim to be agnostic so as not to offend either the religious or the non-religious, and I have nothing but contempt for them.
Still, there are worse groups.
Like those trendy assh*les who claim to be "spiritual, not religious" while taking a break from sniffing their own farts.