Interesting. Guess what book is on top of the pile next to my computer? Yes, “Heretics and Believers.” You are referring to p. 8, although he may go on to discuss the subject more later.
I think Arwing covered the current Catholic position in the previous post. To summarize or paraphrase it, “perfect” contrition is sorrow for sins because they have offended God; “imperfect” contrition is sorrow for sins primarily because you fear God’s punishment. Either is acceptable in confession, although the Act of Contrition, which is said after confessing your sins, includes the phrase “I am sorry for my sins because of thy just punishments [imperfect contrition], but MOST OF ALL because they have offended Thee, my God, who art all good and deserving of all love…” [perfect contrition]. Note that as Arwing quoted in #1452 “perfect” contrition–outside confession–absolves you of mortal sin in certain circumstances (for example, you know you are dying, and you say an Act of Contrition–perfect contrition); “imperfect” contrition does not absolve you of mortal sins–you need to go to confession for that, dying or not!
Having said all that, I am curious about Peter Marshall’s own background. He was raised in the Orkney Islands; hardly a stronghold of Catholicism, and yet there does seem to be a presence: http://www.catholicchurchorkney.org.uk/catholic_orkney.html Another web site gives the % of Catholics, etc. https://www.nrscotland.gov.uk/files/statistics/occasional-paper-10-table3.pdf and “no religion” is roughly half of Orkney; Church of Scotland is about 33%, and Catholic is 0.5 % to 8.6% depending on the parish. From what I have gleaned from a quick reading of some web sites, the Reformation in the Orkneys left a lot of the traditional religion intact. And keep in mind it didn’t become part of Scotland until 1472, not that long before the Reformation (it belonged to Denmark before that). I can’t imagine that the Scottish gov. (or church) cared much about the remote Orkneys in the late 15th and 16th centuries…or probably until the naval base at Scapa Flow was established. (A great uncle of mine in the Royal Navy died at Scapa Flow in WW I–his ship exploded.) So I would guess that the Orkneys were “Protestant” officially, but I would guess they kept a lot of Catholic traditions, etc.
So who cares, right? Well, on a subject like the Reformation, I always like to know if an author has an ax to grind; even after 500 years, scholars take sides. So Peter Marshall? I don’t know. I assume he’s Protestant since he writes almost exclusively about the Reformation (I have almost all his books). Does that skew his presentation? I don’t know. But I’m guessing he got interested in the subject because of the lingering Catholic traditions in the Orkneys.