It's simple but it makes sense.
Gnosticism, for our purposes, is the belief that there is an absolute knowledge, so that one can say definitely that something is or is not true. So, in this case, somebody on the far “gnostic” side of our graph would argue that the statement “There is a God” can be proven to be 100 per cent valid or invalid; somebody on the far “agnostic” side, would argue that the same statement can never be proven to any degree of accuracy because it’s impossible to know. ... Is this the definitive way of charting people’s religious positions? Of course not. But it provides a helpful mental image when trying to discuss people’s views. A “strong theist” – let’s say the Pope – will be found at the maximum poles of gnosticism and theism: there is absolutely a God. Whether it exists and can be known is completely beyond doubt. A “strong atheist” hangs around the maximums of gnosticism and atheismThe rest of the accompanying article is good also.