The construction of "Known but to God"
The Tomb of the Unknown Solider has the engraving "KNOWN BUT TO GOD", as presumably no man knows his name, but shouldn't it read "unknown, but to God", as the default for everyone is "unknown", with the exception "but to God"?
Is the construction older? How should it be parsed?
Solution 1:
In the phrase
Known but to God
but functions as an adverb, and, as such, it means only. Thus, the inscription could very well read:
Known only to God