The visible spectrum which the human eye can observe is limited and we cannot imagine the colors outside of that spectrum. The same kind of constraint would logically apply to our brain aswell. Humans are only capable of understanding a small fraction of the laws of the universe. This means that there most likely is something beyond our materialistic world that we are simply not able to observe or comprehend. Since we cannot prove what this is with logical reasoning nobody can know for certain what it is, we can only make assumptions. Therefore agnositicism is the closest thing to an absolute truth we can get.