They do.

They unsettled mine horribly.

The rationalist made me question whether reason was of any use whatever; and when I had finished Herbert Spencer I had got as far as doubting (for the first time) whether evolution had occurred at all.

As I laid down the last of Colonel Ingersoll's atheistic lectures the dreadful thought broke across my mind, "Almost thou persuadest me to be a Christian." I was in a desperate way.
This odd effect of the great agnostics in arousing doubts deeper than their own might be illustrated in many ways.

I take only one.