Complex sentence: The importance which Justin attaches to the evidence of prophecy shows his estimate of the Old Testament Scriptures, however, the scriptural authority he attributes to the "memoirs of the apostles" is less certain.
Split into simpler sentences: The importance which Justin attaches to the evidence of prophecy shows his estimate of the Old Testament Scriptures. However, the scriptural authority he attributes to the "memoirs of the apostles" is less certain.