怪力乱神を語らず
(Kairyoku ranshin wo katarazu; “Speaking not of spirits and demons”)

Definition:

A wise person does not indulge in talking about irrational or unreasonable things; a great person does not dabble in conspiracy or superstition. When you make an assertion, you need to make it based on facts and evidence rather than vague supposition or unconfirmed impressions – especially if you’re in a position where your words have power.

Breakdown:

This simple phrase is completed by the verb 語る (kataru), “to talk about,” “to tell (a story),” in imperfective form and with negative suffix ず (zu) in conclusive form. The particle を (wo) tells us the object of this verb; in this case, compound noun (and yojijukugo) 怪力乱神 (kai ryoku ran shin), literally “mysterious power disordered god(s),” but taken together, referring more generally to mysterious or supernatural phenomena.

Notes:

This admonition comes to us from the Analects of Confucious (論語, Japanese Rongo).

There are contexts in which 怪力 may be pronounced kairiki. This saying is not one of them.

Example sentence:

「カナダの存在はただの都市伝説だなんていう陰謀説は遊びにしたら面白いかもしれないけど、さすがに常識に逆らってるから、友達の間でしか話さない方がいい。怪力乱神を語らずって言うんだ」

(“Canada no sonzai wa tada no toshi densetsu da nante iu inbousetsu wa asobi ni shitara omoshiroi kamoshirenai kedo, sasuga ni joushiki ni sakaratteru kara, tomodachi no aida de shika hanasanai hou ga ii. Kairyoku ranshin wo katarazu tte iu nda.”)

[“It might be entertaining to play around with conspiracy theories, like saying that Canada is just an urban legend. But it does go against common sense, and it’s something best saved for when you’re with friends. In other situations there’s no call for Bigfoot stories.”]