▁other ▁hand , ▁for ▁all ▁composite ▁numbers ▁n , ▁ 2 · n ▁> ▁ 2 ▁+ ▁n ▁is ▁true , ▁because ▁none ▁of ▁the ▁counter examples ▁are ▁composite ▁numbers . ▁This ▁indicates ▁the ▁importance ▁of ▁the ▁domain ▁of ▁disc ourse , ▁which ▁spec ifies ▁which ▁values ▁n ▁can ▁take . ▁In ▁particular , ▁note ▁that ▁if ▁the ▁domain ▁of ▁disc ourse ▁is ▁restricted ▁to ▁consist ▁only ▁of ▁those ▁objects ▁that ▁satisfy ▁a ▁certain ▁predicate , ▁then ▁for ▁universal ▁quant ification ▁this ▁requires ▁a ▁logical ▁conditional . ▁For ▁example , ▁For ▁all ▁composite ▁numbers ▁n , ▁ 2 · n ▁> ▁ 2 ▁+ ▁n ▁is ▁log ically ▁equivalent ▁to ▁For ▁all ▁natural ▁numbers ▁n , ▁if ▁n ▁is ▁composite , ▁then ▁ 2 · n ▁> ▁ 2 ▁+ ▁n . ▁Here ▁the ▁" if ▁... ▁then " ▁construction ▁indicates ▁the ▁logical ▁conditional . ▁ ▁Not ation ▁ ▁In ▁symbol ic ▁logic , ▁the ▁universal ▁quant ifier ▁symbol ▁ ▁( an ▁invert ed   " A " ▁in ▁a ▁sans - ser if ▁font , ▁Unicode   U + 2 2 0 0 ) ▁is ▁used ▁to ▁indicate ▁universal ▁quant ification . ▁It ▁was ▁first ▁used ▁in ▁this ▁way ▁by ▁Ger hard ▁Gent zen ▁in ▁ 1 9 3 5 , ▁by ▁anal ogy ▁with ▁Giuseppe ▁Pe ano ' s ▁ups ide - down ▁E ▁notation ▁for ▁exist ential ▁quant ification ▁and ▁the ▁later ▁use ▁of ▁Pe ano ' s ▁notation ▁by ▁Ber tr and ▁Russell . ▁ ▁For ▁example , ▁if