Healy continues that Book IV is generally considered to embody the oldest portions of the oracles, and while many of the older critics saw in it elements which were considered to be Christian, it is now looked on as completely Jewish. Book V has given rise to many divergent opinions, some claiming it as Jewish, others as the work of a Christian Jew, and others as being largely interpolated by a Christian. It contains so little that can be considered Christian that it can safely be set down as Jewish. Books VI and VII are admittedly of Christian origin. Some authors (Mendelssohn, Alexandre, Geffcken) describe Book VI as an heretical hymn, but this contention has no evidence in its favour. It dates most probably from the third century AD. Books I and II are regarded as a Christian revision of a Jewish original. Book VIII offers peculiar difficulties; the first 216 verses are most likely the work of a second century AD Jew, while the latter part (verses 217-500) beginning with an acrostic on the symbolic Christian word "Icthus" is undoubtedly Christian, and dates most probably from the third century AD. In the form in which they are now found the other four books are probably the work of Christian authors. Books XII and XIII are from the same pen, XII being a revision of a Jewish original. Book XI might have been written either by a Christian or a Jew in the third century AD, and Book XIV of the same doubtful provenance dates from the fourth century AD. The general conclusion is that Books VI, VII, and XIII and the latter part of Book VIII are wholly Christian. Books I, II, XI, XII, XIII, and XIV received their present form from a Christian. The peculiar Christian circle in which these compositions originated cannot be determined, neither can it be asserted what motive prompted their composition except as a means of Christian propaganda.