…than to be shot down.
怜悧なる頭には閉じたる口あり
(Reiri naru atama ni wa tojitaru kuchi ari;
“In the clever head, a closed mouth.”)
Definition:
A wise person doesn’t speak any more than necessary, and thus doesn’t say foolish, boring, or pointless things. “Silence at the proper season is wisdom.”
Breakdown:
We begin this complete sentence with the compound noun 怜悧 (reiri), “cleverness,” “wisdom.” This is followed by the copular particle なり (nari) in prenominal form as なる, allowing it to attach to and modify the noun 頭 (atama), “head.” Next we get the locational particle に (ni), doubled up with the topic marker particle は (wa); that is to say, the topic of this phrase is “as for in-the-head-that-is-wise.”
The comment on this topic centers on the noun 口 (kuchi), “mouth.” It is preceded by the intransitive verb 閉づ (todzu), “to close,” in conjunctive form and taking the auxiliary verb たり (tari), which indicates that the verb it modifies is in a conclusive or continuative state; also in prenominal form so that it may prefix the noun. And following kuchi is the copular verb あり (“to be”), in conclusive form.
Notes:
This obscure saying is attributed to an admiral of the Imperial Japanese Navy, Yamamoto Isoroku; perhaps it’s appropriate then that he died thanks to a broken code allowing his plane to be targeted by the US Air Force.
Example sentence:
「学生時代は社会不安のせいであまり口を利かなかったが、そのせいで怜悧なる頭には閉じたる口ありで控えているのだと思われて、クラスメイトには格好良いと分不相応な称賛を受けていた」
(“Gakusei jidai wa shakai fuan no sei de amari kuchi wo kikanakatta ga, sono sei de reiri naru atama ni wa tojitaru kuchi ari de hikaeteiru no da to omowarete, kurasumeito ni wa kakkou ii to bunfusouou na shousan wo uketeita.”)
[“When I was a student I almost never spoke out of social anxiety. But people thought that I was holding back because of how the wise speak only when necessary, and my classmates showered me with undeserved praise about how cool I was.”]
landofnudotcom 
Wonder is the seed of knowledge
(France is bacon)
大疑は大悟の基
(Taigi wa taigo no motoi;
“Great doubts are the foundation of great enlightenment”)
Definition:
Great doubt is the first step toward great realizations. Doubt leads to asking questions, which leads to seeking answers, which – in theory at least – eventually leads to finding answers that leave you with a broader and deeper understanding.
Breakdown:
We begin with the compound noun 大疑 (taigi), “big doubt,” marked by the particle は (wa) as the topic of discussion. The comment on this topic is another noun phrase; compound noun 大悟 (taigo), “big revelation,” marked by the associative particle の (no) as attaching to and possessing the noun 基 (motoi), “foundation.” One may imagine an elided copula to make the phrase into a complete sentence.
Notes:
Keep in mind that 悟 isn’t just any random realization; it refers specifically to Buddhist enlightenment about the true nature of the universe.
基 may also be read as moto without any change in meaning; my sources seem evenly split on which is considered the “main” reading and which the alternate. Variant phrasings may make the same general point with a double negative, such as 疑わぬ者に悟りなし (utagawanu mono ni satori nashi), “for those who do not doubt, there is no satori.” Another variant takes this form but replaces 疑わぬ with 迷わぬ (mayowanu), i.e. “getting lost” instead of “doubting.”
One possibly-interesting footnote is that, since for my current いろは-ordered series I’ve been trying to use phrases from the major iroha karuta sets, my original plan was to do a write-up for a saying that goes 大食上戸の餅食らい (taijiki jouto no mochi-kurai). (This is the た entry in the Osaka/Nagoya set; I’ve already used the entries for the Edo and Kyoto sets.)
The thing is, there doesn’t seem to be much reliable information on this phrase online. None of my regular sources include it, and a further search only pointed me to a handful of rambling blog posts that give opinions without citing authoritative sources. There’s a chance that a trip to the East Asian collection at the local university library would provide something more solid (they have several books on kotowaza), but in the end it was simply more efficient to choose a better-documented phrase.
Example sentence:
「大疑は大悟の基だと専門家の主張を躱すことは決して悪いことではないけど、自分の考えに対する疑問も持つべきだ」
(“Taigi wa taigo no motoi da to senmonka no shuchou wo kawasu koto wa kesshite warui koto de wa nai kedo, jibun no kangae ni tai suru gimon mo motsu beki da.”)
[“It’s not necessarily a bad thing to say that ‘great doubt is the basis of great understanding’ to deflect what experts have declared, but it is necessary to entertain questions about your own thinking.”]