The arrangement into three triads of fourteen generations each was obviously in the nature of a memoria technica. The periods embraced by the three groups were, it may be noted, of very unequal length; and the actual omission of names in one of them, makes it possible that the others may have been treated in the same way.
(1) From the birth of Abraham to the birth of David, taking the dates supplied by the received chronology of the Old Testament. B.C. 1996-1085.
(2) From the birth of David to the Captivity. B.C. 1085-588.
(3) From the Captivity to the birth of Jesus. B.C. 588-4.
There remains the further question, how we are to reconcile the genealogy given by St. Matthew with that given by St. Luke (Luke 3:23-38). This will, it is believed, be best dealt with in a short Excursus in the Notes on that Gospel. Here it may be sufficient to note that the difference between the two is, at least, strong presumptive evidence that neither of the two Evangelists had seen the record of the other. It is otherwise hardly conceivable that the element of difficulty which these differences involve should have been introduced by one or the other without a word of explanation. Each, it may be presumed, copied a document which he found, and the two documents were drawn up on a different plan as to the ideas of succession recognised in each of them.