Do they mean the same when used in a sentence?
Example:
A scream would occasionally escape from her, only to be absorbed by the dark metallic walls.
A scream would occasionally escape from her, but only to be absorbed by the dark metallic walls.
Do both sentences mean the same? If not, what would be the difference?
This is not a special case of but, only or but only. The words but and only mean just the same here as elsewhere in an English sentence.
1 used to introduce a phrase or clause contrasting with what has already been mentioned: he stumbled but didn’t fall
2 [with negative or in questions] used to indicate the impossibility of anything other than what is being stated: one cannot but sympathize
Let there be no confusion here with the secondary definition of but that is not relevant here (used to indicate the impossibility of anything other than what is being stated: one cannot but sympathize) -- use the primary: (used to introduce a phrase or clause contrasting with what has already been mentioned: he stumbled but didn’t fall)
The sentences do not mean the same thing.
