たるゆえん
(Taru yuen)
the reason for being / what makes (X) an X.
Connection rules
- +Noun (role / identity) + たるゆえん + predicate.
- +Very literary / classical — 'the essence of being X'.
- +Used in reflective or moralizing statements.
Examples
1.
考えることこそ、人間たるゆえんだ。

Kangaeru koto koso, ningen taru yuen da.
Thinking is what makes us human.
「the reason for being / what makes (X) an X」
2.
誠実さが、教師たるゆえんだ。

Seijitsu sa ga, kyoushi taru yuen da.
Sincerity is what makes a teacher a teacher.
「the reason for being / what makes (X) an X」
Practice
His ability to maintain composure in a crisis is what makes him a true leader.
危機に際しても冷静さを保てるところこそ、彼が___だ。
Romaji also accepted