We have had already occasion to observe that Zen teaches Buddha-nature, which all sentient beings are endowed with. The term 'Buddha-nature,'[FN#165] as accepted generally by Buddhists, means a latent and undeveloped nature, which enables its owner to become Enlightened when it is developed and brought to actuality.[FN#166] Therefore man, according to Zen, is not good-natured nor bad-natured in the relative sense, as accepted generally by common sense, of these terms, but Buddha-natured in the sense of non-duality. A good person (of common sense) differs from a bad person (of common sense), not in his inborn Buddha-nature, but in the extent of his expressing it in deeds. Even if men are equally endowed with that nature, yet their different states of development do not allow them to express it to an equal extent in conduct. Buddha-nature may be compared with the sun, and individual mind with the sky. Then an Enlightened mind is like the sky in fair weather, when nothing prevents the beams of the sun; while an ignorant mind is like the sky in cloudy weather, when the sun sheds faint light; and an evil mind is like the sky in stormy weather, when the sun seems to be out of existence. It comes under our daily observation that even a robber or a murderer may prove to be a good father and a loving husband to his wife and children. He is an honest fellow when he remains at home. The sun of Buddha-nature gives light within the wall of his house, but without the house the darkness of foul crimes shrouds him. [FN#165] For a detailed explanation of Buddha-nature, see the chapter entitled Buddha-nature in Sho-bo-gen-zo. [FN#166] Mahaparinirvana-sutra may be said to have been written for the purpose of stating this idea. 9. The Parable of the Robber Kih.[FN#167] Chwang Tsz (So-shi) remarks in a humorous way to the following effect: "The followers of the great robber and murderer Kih asked him saying: 'Has the robber also any moral principles in his proceedings?' He replied: 'What profession is there which has not its principles? That the robber comes to the conclusion without mistake that there are valuable deposits in an apartment shows his wisdom; that he is the first to enter it shows his bravery; that he makes an equal division of the plunder shows his justice; that he never betrays the fellow-robbers shows his faithfulness; and that he is generous to the followers shows his benevolence. Without all these five qualities no one in the world has ever attained to become a great robber.'" The parable clearly shows us Buddha-nature of the robber and murderer expresses itself as wisdom, bravery, justice, faithfulness, and benevolence in his society, and that if he did the same outside it, he would not be a great robber but a great sage.