2. CONSTANCY OF THE CHAIN OF NARRATORS
It is well-known that no report, in the science of hadith, is accepted unless it gives the full chain of narrators upto the Holy Prophet (SAWS). Each narrator from this chain is first scrutinized on the touch-stone of his credibility as discussed above. But even if all the narrators of a chain are found to be reliable, it is not enough to hold the tradition as authentic. It must be proved that the chain is constant and no narrator has been missed in between. If it is found that some narrator has been missed at any stage, the tradition is held to be unreliable. To ensure the constancy of the chain, it is necessary to know about each narrator whether it is possible for him historically to meet the person from whom he claims to hear the tradition.