“The so-called evils are evils only in relation to a certain thing, and that which is evil in relation to a certain existing thing, either includes the non-existence of that thing or the non-existence of some of its good conditions.”

Source: Guide for the Perplexed (c. 1190), Part III, Ch.10

Source: Guide for the Perplexed (c. 1190), Part III, Ch.11

Motto of the work written by Hesse, and attributed to an "Albertus Secundus"
The Glass Bead Game (1943)
Context: For although in a certain sense and for light-minded persons non-existent things can be more easily and irresponsibly represented in words than existing things, for the serious and conscientious historian it is just the reverse. Nothing is harder, yet nothing is more necessary, than to speak of certain things whose existence is neither demonstrable nor probable. The very fact that serious and conscientious men treat them as existing things brings them a step closer to existence and to the possibility of being born.

Source: Succubus Shadows

XII. The origin of evil things; and that there is no positive evil.
On the Gods and the Cosmos
Context: If evil exists it must exist either in Gods or minds or souls or bodies. It does not exist in any God, for all god is good. If anyone speaks of a "bad mind" he means a mind without mind. If of a bad soul, he will make the soul inferior to body, for no body in itself is evil. If he says that evil is made up of soul and body together, it is absurd that separately they should not be evil, but joined should create evil.

5th Public Talk, Amsterdam, The Netherlands (30 May 1967)
1960s

On the Hydrogen bomb in a minority addendum http://honors.umd.edu/HONR269J/archive/GACReport491030.html (co-authored with I. I. Rabi) to an official General Advisory Committee report for the Atomic Energy Commission (30 October 1949)
Context: Such a weapon goes far beyond any military objective and enters the range of very great natural catastrophes. By its very nature it cannot be confined to a military objective but becomes a weapon which in practical effect is almost one of genocide. It is clear that the use of such a weapon cannot be justified on any ethical ground which gives a human being a certain individuality and dignity even if he happens to be a resident of an enemy country... The fact that no limits exist to the destructiveness of this weapon makes its very existence and the knowledge of its construction a danger to humanity as a whole. It is necessarily an evil thing considered in any light.

XII. The origin of evil things; and that there is no positive evil.
On the Gods and the Cosmos