There was a time not too long ago when one with a scientific mind would have read this statement and in humility would agree how truly small our knowledge is in comparison to that which we do not know and would have marveled at what was yet to be learned.
Each discovery shows that science is able to assimilate more evidence as it appears. Unlike religion, which pretends that new knowledge doesn't mean anything at all; the 'facts' have already been decided in dusty old books written by people whose imaginations couldn't have grasped the scientific method...
Today the scientific mind reads the same statement and in it's arrogance sees it as an attack, and lashes out against the inferior ideology that launched it. All the while marveling at it's superior knowledge and intellect.
There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don’t know. But there are also unknown unknowns. There are things we don’t know we don’t know.
Donald Rumsfeld