In common with other moralists, Saadi reiterates the maxim that learning and virtue, precept and practice, should ever go hand in hand. "Two persons," says he, "took trouble in vain: he who acquired wealth without using it, and he who taught wisdom without practising it." Again: "He who has acquired knowledge and does not practise it, is like unto him that ploughed but did not sow." And again: "How much soever you may study science, when you do not act wisely, you are ignorant. The beast that they load with books is not profoundly wise and learned: what knoweth his empty skull whether he carrieth fire-wood or books?" And yet again: "A learned man without temperance is like a blind man carrying a lamp: he showeth the way to others, but does not guide himself." Ingratitude is denounced by all moralists as the lowest of vices. Thus Saadi says: "Man is beyond dispute the most excellent of created beings, and the vilest animal is the dog; but the sages agree that a grateful dog is better than an ungrateful man. A dog never forgets a morsel, though you pelt him a hundred times with stones. But if you cherish a mean wretch for an age, he will fight with you for a mere trifle." In language still more forcible does a Hindu poet denounce this basest of vices: "To cut off the teats of a cow;[18] to occasion a pregnant woman to miscarry; to injure a Brahman--are sins of the most aggravated nature; but more atrocious than these is ingratitude." [18] The cow is sacred among the Hindus. The sentiment so tersely expressed in the Chinese proverb, "He who never reveals a secret keeps it best," is thus finely amplified by Saadi: "The matter which you wish to preserve as a secret impart not to every one, although he may be worthy of confidence; for no one will be so true to your secret as yourself. It is safer to be silent than to reveal a secret to any one, and tell him not to mention it. O wise man! stop the water at the spring-head, for when it is in full stream you cannot arrest it."[19] [19] Thus also Jami, in his _Baharistan_ (Second "Garden"): "With regard to a secret divulged and one kept concealed, there is in use an excellent proverb, that the one is an arrow still in our possession, and the other is an arrow sent from the bow." And another Persian poet, whose name I have not ascertained, eloquently exclaims: "O my heart! if thou desirest ease in this life, keep thy secrets undisclosed, like the modest rose-bud. Take warning from that lovely flower, which, by expanding its hitherto hidden beauties when in full bloom, gives its leaves and its happiness to the winds."