Wir müssen wissen – wir werden wissen

 Emil du Bois-Reymond about "we don't know, we will not know"

Gegenüber den Räthseln der Körperwelt ist der Naturforscher längst gewöhnt, mit männlicher Entsagung sein 'Ignoramus' auszusprechen. Im Rückblick auf die durchlaufene siegreiche Bahn trägt ihn dabei das stille Bewusstsein, dass, wo er jetzt nicht weiss, er wenigstens unter Umständen wissen könnte, und der- einst vielleicht wissen wird. Gegenüber dem Räthsel aber, was Materie und Kraft seien, und wie sie zu denken vermögen, muss er ein für allemal zu dem viel schwerer abzugebenden Wahrspruch sich ent- schliessen: 

‘Ignorabimus!’

Über die grenzen des Naturerkennens : die sieben Welträthsel, Leipzig, 1852, p.45ff

But David Hilbert, opposed this view:

We must not believe those, who today, with philosophical bearing and deliberative tone, prophesy the fall of culture and accept the ignorabimus. For us there is no ignorabimus, and in my opinion none whatever in natural science. In opposition to the foolish ignorabimus our slogan shall be Wir müssen wissen – wir werden wissen ("We must know — we will know.")

Hillel said: 

Say not of a thing which cannot be understood that in the end it will be understood 

(The Father According to Rabbi Nathan p. 117)

Which the commentators explained as:

Rambam: "Do not have your words require a distant explanation and extra examination and [only] then will the listener understand them."

Bartenura: "Do not say something that cannot be heard, for in the end it will be heard": That is to say, do not let your words be unclear, such that it is impossible to understand them immediately and at first perusal; and [do not] rely on that if the listener wants to look into them, in the end, he will understand them. As this will bring people to err from your words, lest they err and come to heresy because of you. Another explanation: Do not reveal your secret, even [saying it aloud] only to yourself, as in the end it will be heard, "since the birds of the sky make the voice travel." And the [correct] textual variant according to this explanation is, "for in the end it will be heard." But Rashi had the variant, "Do not say, 'something that can be heard, in the end it will be heard.'" And [according to this,] it is speaking about the words of Torah: Do not say about a Torah teaching that you can hear now, that you will hear it in the end (later), but rather extend your ears and hear it immediately.

English Explanation of Mishnah Bartenura: a person should make his words clear from the outset, and not speak or write in an unclear manner. Although in the end the matter might be cleared up, in the meanwhile the listener might make mistakes.

Ikar Tosafot Yom Tov: "Rambam does not explain it [this way], but rather that simple words should not be very distant and confound speech. As [Rambam] says [that] your words should not require a far-fetched explanation."

References:

https://www.sefaria.org/Pirkei_Avot.2.4?lang=bi&with=Commentary&lang2=en

https://wellcomelibrary.org/item/b28103555#?c=0&m=0&s=0&cv=50&z=-1.0837%2C0%2C3.1675%2C1.6027