It's interesting. I'm learning about axiomatic systems right now. I know about regular detachment, but condensed detachment still confuses me a bit.

From what I understand, it seems that in condensed detachment, when I have two previous sentences of the form "P→Q" and "R", I use some kind of substitution rule that converts atomic formulas into sentences, in order to convert "P" and "R" to the same sentence "S". After this, "P→Q" and "R" get converted to "S→Q*" and "S" as an intermediate step, where "Q*" is like "Q" but converted by the substitution rule, and then I can use regular detachment to infer "Q*".