理所當(dāng)然（理所當(dāng)然）　

◎ 理所當(dāng)然 lǐsuǒdāngrán

[justifiably; a matter of course; as it ought to be; be both natural and right; it goes without saying; it is what propriety requires] 按道理應(yīng)該如此

就把來結(jié)識了這位大哥,也是理所當(dāng)然。——明· 馮夢龍《醒世恒言》