I was reading documentation about the soundness and completeness of logic formal systems.
Consider the following $$\vdash_S \phi$$
where ##S## is the proof-system making part the formal system and ##\phi## is a wff (well formed formula) of the formal language. Note the blank on left of the turnstile symbol ##\vdash_S##, as far as I can tell it actually represents the empty set.
So what does it mean ? I guess it actually means ##\phi## is a theorem of the formal system, i.e. there is a...