He could drag a new culprit to light and immolate a second victim.

That he refrained may have been owing, as we have supposed most likely, to his continued ignorance that the Dr.
Du Moulin now going about in Oxford and in London, so near himself, was the original and principal culprit; or, if he did have any suspicions of the fact, there may have been other reasons, in and after 1655, for a dignified silence.
[Footnote 1: Wood's Fasti, II.

195.] In proceeding from the month of August 1655, when Milton published his _Pro Se Defensio_, to his life through the rest of Oliver's Protectorate, it is as if we were leaving a cluster of large islands that had detained us long by their size and by the storms on their coasts, and were sailing on into a tract of calmer sea, where the islands, though numerous, are but specks in comparison.

The reason of this is that we are now out of the main entanglement of the Salmasius and Morus controversy.

Milton had taken leave of that subject, and indeed of controversy altogether for a good while.
In the original memoirs of Milton due note is taken of this calm in his life after his second castigation of Morus.