“For centuries knowledge meant proven knowledge… Einstein's results again turned the tables and now very few philosophers or scientists still think that scientific knowledge is, or can be, proven knowledge. But few realize that with this the whole classical structure of intellectual values falls in ruins and has to be replaced.”

1880s, Agnosticism (1889)
Context: The extent of the region of the uncertain, the number of the problems the investigation of which ends in a verdict of not proven, will vary according to the knowledge and the intellectual habits of the individual agnostic. I do not very much care to speak of anything as unknowable. What I am sure about is that there are many topics about which I know nothing, and which, so far as I can see, are out of reach of my faculties. But whether these things are knowable by any one else is exactly one of those matters which is beyond my knowledge, though I may have a tolerably strong opinion as to the probabilities of the case.

On War (1832), Book 2

Source: 1960s, Beyond Economics: Essays on Society, 1968, p. 142

A 713, B 741
Critique of Pure Reason (1781; 1787)

Friedrich Schleiermacher, On The Social Element in Religion (1799), The German Classics of the Nineteenth and Twentieth Centuries, Volume 5 http://www.gutenberg.org/ebooks/12888
Context: But the imparting of religion is not to be sought in books, like that of intellectual conceptions and scientific knowledge. The pure impression of the original product is too far destroyed in this medium, which, in the same way that dark-colored objects absorb the greatest proportion of the rays of light, swallows up everything belonging to the pious emotions of the heart, which cannot be embraced in the insufficient symbols from which it is intended again to proceed. Nay, in the written communications of religious feeling, everything needs a double and triple representation; for that which originally represented, must be represented in its turn; and yet the effect on the whole man, in its complete unity, can only be imperfectly set forth by continued and varied reflections. It is only when religion is driven out from the society of the living, that it must conceal its manifold life under the dead letter. Neither can this intercourse of heart with heart, on the deepest feelings of humanity, be carried on in common conversation.

Science and Wisdom (1954), p. 109.

Majlisi, Bihārul Anwār, vol.1, p. 183.

Source: 1960s, Beyond Economics: Essays on Society, 1968, p. 142