to describe one's words as rational and convincing; cogently argued; sounds reasonable
Definitions (粵典–words.hk)
語句
講嘅嘢成道理而且令人信服 to deliver a claim in a rational and convincing manner
佢講嘢言之成理，抵佢做大狀。
佢讲嘢言之成理，抵佢做大状。
keoi5 gong2 je5 jin4 zi1 sing4 lei5, dai2 keoi5 zou6 daai6 zong6. His words are charmingly sensible, I see all these tuition spent on law school haven't gone wasted.