What is the meaning of the River of Doubt?

I have told you of the great black river here, which is not Lethe. 

I was sitting one day near its bank, thinking of the sad past and sadder future—the turbid waves rolled heavily by.

Groans broke upon the silence about me. 

I started and perceived a strange figure, strangely occupied. 

It was a man of commanding aspect, handsome even, but in most painful plight. 

He sat by the river washing his hands, which dripped with blood. 

But for all his washing, the dread crimson would not leave his fingers—as soon as he lifted them above the water, the red blood trickled down afresh. It was a pitiful sight.

He seemed to be aware of my presence, for he turned upon me suddenly, saying, What is truth? 

I did not reply at once, feeling it to be a question that should not be answered lightly—but raising his voice, he repeated impatiently, What is truth?

Well, I said, it is a truth, and a sad one, that it is too late now for us to be seeking the truth.

This answer did not appear to satisfy him. 

He shook his head, turning away. 

And again, he set to washing his hands.

I endeavoured to draw him into conversation. 

I seemed suddenly to know that he was one of those doubly miserable souls who had seen the Son of Man face-to-face and heard him speak, and I was most anxious to hear what he might have to tell me, but there was no turning him from his frightful occupation.

I left him after a while. 

Who he was I knew without the testimony of his purple-bordered toga and the ring on his finger—Pontius Pilate!

He shuns the city of the Jews and spends his time by the river washing his hands. 

But of every passer-by he asks the question, What is truth? 

Whatever answer he receives, he shakes his head—it is not general truths he wants to know about, but the Truth—Truth Absolute, and that is not known here. 

And do you perceive the cutting contrast? 

Pilate inquiring about truth, yet washing his hands in the river of falsehood!

Letters from Hell