Knowledge is like unto wings for the being (of man) and is like a ladder for ascending. To acquire knowledge is incumbent upon all, but of those sciences which may profit the people of the earth, and not such sciences as being in mere words and end in mere words. The possessors of sciences and arts have a great right among the people of the world. Indeed, the real treasury of man is his knowledge. Knowledge is the means of honor, prosperity, joy, gladness, happiness and exaltation.—Tablet of Tajallíyát. Treatment of Criminals In a talk on the right method of treating criminals, ‘Abdu’l-Bahá spoke as follows:— ... the most essential thing is that the people must be educated in such a way ... that they will avoid and shrink from perpetrating crimes, so that the crime itself will appear to them as the greatest chastisement, the utmost condemnation and torment. Therefore no crimes which require punishment will be committed.... ... if someone oppresses, injures, and wrongs another, and the wronged man retaliates, this is vengeance, and is censurable. ... If ‘Amr dishonours Zaid, the latter has not the right to dishonour ‘Amr; if he does so, this is vengeance, and is very reprehensible. No, rather he must return good for evil, and not only forgive, but also, if possible, be of service to his oppressor. This conduct is worthy of man; for what advantage does he gain by vengeance? The two actions are equivalent; if one action is reprehensible, both are reprehensible. The only difference is that one was committed first, the other later. But the community has the right of defense and of self-protection; moreover, the community has no hatred nor animosity for the murderer: it imprisons or punishes him merely for the protection and security of others. ... Thus when Christ said: “Whosoever shall smite thee on the right cheek, turn to him the left one also,” it was for the purpose of teaching men not to take personal revenge. He did not mean that if a wolf should fall upon a flock of sheep and wish to destroy it, that the wolf should be encouraged to do so. No, if Christ had known that a wolf had entered the fold and was about to destroy the sheep, most certainly he would have prevented it. ...