Why is SD+ so difficult???

[Marie120]

I understand SD, but SD+ is eluding me..

[Math Is Hard]

what's SD and SD+?

[hitssquad]

SD and SD+ stand for Sentential Derivation:
http://www.lawrence.edu/dept/philosophy/research/ryckmant/logic/sententi.htm


The sentential, or propositional, logic SL consists of a sentential language, SL, a semantic interpretation of that language, and a sentential derivation system, SD (and SD+).

One might use SL to examine the logical relations among molecular or (compound) sentences generated from atomic (or simple) sentences.

From SL's perspective, only molecular sentences have structure or form, and, therefore, SL is a logic that deals with relations obtaining among molecular sentences in virtue of their structure or form.

[Marie120]

If what you're seeking to prove can be proven using SD+, then it can be proven using SD. Since SD+ basically gives rules that work as shortcuts, shouldn't it be easier for me to prove that a set of sentences is inconsistent using SD+ and SD than it currently is?