Truth, (sacca or taccha) is speech, writing, notions or an understanding that corresponds with reality and which, if comprehended correctly, can lead one to a more accurate and complete perception of that reality. There are two types of truth; mundane and supermundane. If one says: `It is raining' and it is raining, this statement can be said to be true. However, this is only a mundane truth because it is of limited value. If, on the other hand, one says: `Craving causes dissatisfaction' and it actually does, this can be said to be a supermundane truth because if understood and taken into account it could lead to a radical change in one's attitude, one's life and ultimately, one's destiny. Some truths can be partial in that they correspond to some aspects of a reality but not others. However, one truth cannot contradict another. If a person says: `Two plus two equals four' and another says: `Two plus two equals five,' one or the other of these two statements must be false. Thus the Buddha said: `Truth is one' (ekaü hi saccaü, Sn.884). The most significant supermundane truths taught by the Buddha are the Four Noble Truths. Concerning the importance of understanding these truths the Jàtaka says: `One who would give up wealth to save a limb, or sacrifice a limb to save his life, should be prepared to give up wealth, limb, life, indeed everything, for the  Truth' (Ja.V,500)

            The Buddha laid the greatest stress on speaking truthfully. The first and most important characteristic of Right Speech is that it be true to the best of one's understanding. Of speech that accords with the Dhamma he said: `One should refrain from false speech. When summoned before the court, an inquiry, a family gathering, a guild or the king, and asked ßSo, good man, tell us what you know.û If he does not know, he says ßI don't know.û If he knows, he says ßI know.û If he did not see, he says ßI didn't see,ûand if he saw he says ßI saw.û He does not knowingly lie for his own advantage or another's advantage or for some trifling gain' (M.I,288). See Consistency and Faithfulness.