The evil that is in the world always comes of ignorance, and good intentions may do as much harm as malevolence, if they lack understanding. On the whole men are more good than bad; that, however, isn't the real point. But they are more or less ignorant, and it is this that we call vice or virtue; the most incorrigible vice being that of an ignorance which fancies it knows everything and therefore claims for itself the right to kill. There can be no true goodness, nor true love, without the utmost clear-sightedness.

The evil in the world comes almost always from ignorance, and goodwill can cause as much damage as ill-will if it is not enlightened. People are more often good than bad, though in fact that is not the question. But they are more or less ignorant and this is what one calls vice or virtue, the most appalling vice being the ignorance that thinks it knows everything and which consequently authorizes itself to kill. The murderer's soul is blind, and there is no true goodness or fine love without the greatest possible degree of clear-sightedness.

Evil is ignorance.

Ignorance, the root and stem of every evil.

Ignorance, the root and stem of all evil.

All the great evils which men cause to each other because of certain intentions, desires, opinions, or religious principles, are likewise due to non-existence, because they originate in ignorance, which is absence of wisdom.

Much of the evil in this world is due to the fact that man, in general, is hopelessly unconscious.

All the evils that men cause to each other because of certain desires, or opinions or religious principles, are rooted in ignorance. [All hatred would come to an end] when the earth was flooded with the knowledge of God.

It is on account neither of God's weakness nor ignorance that evil comes into the world, but rather it is due to the order of his wisdom and the greatness of his goodness that diverse grades of goodness occur in things, many of which would be lacking if no evil were permitted. Indeed, the good of patience would not exist without the evil of persecution; nor the good of preservation of life in a lion if not for the evil of the destruction of the animals on which it lives.

At the root of all the harm we cause is ignorance.

Goodness without wisdom always accomplishes evil.

Most of the evil in this world is done by people with good intentions.

Knowledge becomes evil if the aim be not virtuous.

The knowledge of evil is inadequate knowledge

Ethics Book IV, proposition 64