After listening to a long lecture, Friday asked a question that took Crusoe aback. Here is CliffsNotes summarising that particular scene:
"If God, much strong, much might as Devil, why God no kill Devil, so make him no more do wicked?" Crusoe, not feeling qualified to answer Friday's question suggested that perhaps God was waiting for the Devil to repent and be pardoned.
Why didn't Crusoe feel qualified to answer the question?
We need to look at this incident at two levels. The specific question is answered by the fact that Crusoe is not a theological expert. But there is a wider point being made about whether he needs to be one, and therefore whether Friday can truly enter into the faith, in the absence of any church structure as such. Defoe is contributing to a broad and important debate about the Christian religion.
(Small note: The quoted summary says that Crusoe suggests God may eventually pardon the Devil. This is wrong. Crusoe says that God will punish the Devil at the end of time, not right now. It is Friday who comes up with the idea of universal pardon, which Crusoe rejects on the grounds that Christ became human in order to save humans, not fallen angels.)
In the immediate moment, Crusoe is taken aback by Friday's question -
I was strangely surpriz'd at his Question, and after all, tho' I was now an old Man, yet I was but a young Doctor, and ill enough quallified for a Casuist, or a Solver of Difficulties: And at first I could not tell what to say, so I pretended not to hear him, and ask'd him what he said?
The reason he does not have an immediate answer is that he is not a theologian who has been trained up to respond to these sorts of challenges. He has "a competent Share of Learning, as far as House-Education, and a Country Free-School generally goes", which is to say that he has received little formal education. Here, "a young Doctor" means that he has not spent much time in the moral instruction of others, and a "Casuist" is a disparaging reference to people who are occupied with overly complicated theoretical wrangling over moral issues. Crusoe has access to the text of the Bible, and has a general Christian background, but isn't a scholar of religion.
But if we zoom out a bit we find that there is something else going on. Crusoe eventually does feel qualified either to answer the question, or (more probably) to feel confident in deliberately ignoring it. After prayer, Crusoe returns to preach "Faith in our Blessed Lord Jesus". He says:
I had, God knows, more Sincerity than Knowledge, in all the Methods I took for this poor Creature's Instruction, and must acknowledge what I believe all that act upon the same Principle will find, That in laying Things open to him, I really inform'd and instructed my self in many Things, that either I did not know, or had not fully consider'd before; but which occurr'd naturally to my Mind, upon my searching into them.
So he ultimately does feel equipped to tackle doctrine regarding salvation, repentance, etc., although he distinguishes between a practical understanding of living a Christian life, and "Disputes, Wranglings, Strife and Contention" over "Niceties in Doctrine". He says that he could not "see the least Use that the greatest Knowledge of the disputed Points in Religion which have made such Confusions in the World would have been to us, if we could have obtain'd it." He does not necessarily have an answer to Friday's original question - we are not told, and it may be that Defoe saw this as an example of vain speculation, one of those "Niceties in Doctrine" - but he is certainly teaching with new vigour and confidence.
The role of the Devil here is apparently something which one has to accept as part of faith. In Defoe's reading of the Bible, there evidently is a Devil, who has not yet been cast into the lake of fire, but certain questions cannot be resolved by "the meer Notions of Nature" (i.e. by reason alone, without reference to the special revelation of the Christian faith).
The reason for all of this is that Defoe is making a point about faith and the Church. Robinson Crusoe is away from the institutional structure of religion and the state, is not an ordained priest, and there are no bishops or churches or kings in sight. Nonetheless, Defoe posits that in this situation, he could still live in a Christian manner, lead others into the faith, and reach a correct understanding of Christian doctrine thanks to his access to the Bible (and to the illuminating grace of God). The entire episode functions as an illustration of specifically Protestant, and even specifically Presbyterian, understanding. For example, the passage about how he "inform'd and instructed" himself relates to the belief in the "perspicuity of Scripture", expounded in the Westminster Confession of Faith (1641) as:
The whole counsel of God, concerning all things necessary for His own glory, man’s salvation, faith, and life, is either expressly set down in Scripture, or by good and necessary consequence may be deduced from Scripture: unto which nothing at any time is to be added, whether by new revelations of the Spirit, or traditions of men. [...] All things in Scripture are not alike plain in themselves, nor alike clear unto all; yet those things which are necessary to be known, believed, and observed, for salvation, are so clearly propounded and opened in some place of Scripture or other, that not only the learned, but the unlearned, in a due use of the ordinary means, may attain unto a sufficient understanding of them.
This is in contrast to a Catholic understanding, also found within the Anglican tradition, that the Bible is to be interpreted by and through the Church. The point was very thoroughly debated as a foundational issue in the Reformation. Defoe claims by this illustration that someone with only the Bible, and no other apparatus of the Church or civilization in general, could still do perfectly well.
The content of Crusoe's second round of teaching also relates to doctrines which are emphasised in, or unique to, the Protestant/Reformed traditions. We see the role of grace in leading people to faith, and Friday's becoming "a good Christian" is attributed to his faith alone. They feel no need for a priest, and the Church as such is not mentioned: "we had here the Word of God to read, and no farther off from his Spirit to instruct, than if we had been in England." Crusoe does not mention the sacraments, or any formal mode of worship as such. Nor does he appear to miss them. Even if Crusoe thought he could not baptize Friday personally, he doesn't even think, "I really wish someone was here who could do it."
Today's readers might not notice it, but Defoe is giving a spicy-hot take on a very active topic of contemporary conflict.
