"...who had never had but the one..." - why here stands "never"?
In the story of the Treasure Island Jim during his sleep sometimes imagined 'a dreadful seafaring man' like "...now he was a monstrous kind of a creature who had never had but the one leg, and that in the middle of his body".
The meaning of that is "...who had had but the one leg", I suppose.
But what nuances gives here the word "never"?
I have found the same looking structure in the statement of Voltaire:
"I have never made but one prayer to God, a very short one: 'O Lord make my enemies ridiculous.' And God granted it."
So, he had made only one prayer, hadn't he? But why here also "never" is used?