rhyme or reason

Noun

idiomatic in the negative reason uncountable

(idiomatic, chiefly in the negative) Logic; common sense.

Japanese Meaning

論理 / 常識

There seemed to be no rhyme or reason for his sudden departure.

彼の突然の出発には何の道理もなかったようだ。

Sense（1）

(idiomatic, chiefly in the negative) Logic; common sense.

Prices vary considerably from one town to another with no apparent rhyme or reason.

rhyme

（ canonical ）