Oh, how I love relative clauses! They just don't seem to lend themselves to consistent handling in arcing. Relative clauses contain - and often begin with a relative pronoun (e.g. who, that, which). They generally modify an antecedent in a previous clause by adding further description, thus they are not really making a new proposition even though they do comprise a complete subject-predicate clause.

Here's my stab at a general rule of thumb to help gain some consistency: (a) If the relative pronoun is the subject of the relative clause, do not separate the clause as a new arc. However, (b) If the relative clause has a subject other than the relative pronoun, the clause may receive a distinct arc. For example:

(a) v.21-22, "...through the resurrection of Jesus Christ, who has gone into heaven..." Here the relative clause, "who [i.e. Jesus Christ] has gone into heaven" is a complete subject-predicate clause, but the relative pronoun 'who' is the subject of the clause, so the clause functions as a adjective modifying the antecedent, which in this case is Jesus Christ.

Exception: If the relative clause makes an assertion that is vital to the overall argument, you can substitute a personal pronoun for the relative pronoun and add an appropriate conjunction. e.g. one might restate v.21-22 as follows: "Baptism saves you... as it is an appeal to God for a good conscience through the resurrection of Jesus Christ, [who] because he is at the right hand of God with [all things] having been subjected to him. This is only an example of how to make the change; Both the necessity and the accuracy of inserting 'because' is debatable and shows the need to be careful as this could very easily become eisegesis rather than exegesis. Another example of this is in v.19-20, where the NASB assumes the relative pronoun 'who... once were disobedient,' while the ESV supplies a conjunction and a personal pronoun, 'because they were... disobedient."

(b) v.18-19, "...but made alive in the spirit, in which he went and proclaimed to the spirits in prison." Here the subject-predicate of the relative clause is 'he - proclaimed.' The relative pronoun 'which', though it has an antecedent (the spirit) in the preceding clause, is merely the object of the preposition 'in'. Thus the relative clause is making a new assertion and gets a distinct arc.

Looking back over my arcs, I find several places where I did not follow my own rule of thumb, which shows first, I am learning as I go; second, this is not about hard and fast rules; and third, this is far more grammar than I am qualified to present - my high school English teacher is still weeping in sorrow over my work. I would love to have others weigh in on this subject.

At least for the present arc, keeping larger units and relative clauses together helped highlight the main propositions and clarify a rather fuzzy passage.

Note: John Piper has a helpful section on relative clauses in his booklet, Biblical Exegesis. There is a link to this pdf document on the 'learn' page of this website.

Central Idea: (Flowing directly from v.13-17 where Peter states suffering for the sake of righteousness has as its ultimate end, blessing not defeat), Peter now presents Christ as the supreme example of one who knows what it is to suffer for doing good and experience the blessings - indeed, the complete victory, that came as a result. Baptism is the believer's participation in this resurrection victory which was announced over those defeated.

Explanations / Questions:

v.18, ὅτι καὶ (for also..) connects this unit to the previous (v.13-17) as a Comparison (example).

At first, and maybe second glance, v.19-21 seem at best parenthetical, at worst confusingly disconnected. However, Peter has demonstrated such skill in weaving the OT into his own argumentation that we ought to take care to see how this passage fits within both its immediate context and the letter as a whole.

One tool that has helped me see a passage more clearly is to restate the simple subject-predicate clauses, and then fill in the conjunctions:

Christ suffered

in order that

He might bring us to God

in that 

He was put to death in the flesh

yet 

He was made alive in the spirit

as a result

He proclaimed to the spirits

and moreover

just as

A few were safely delivered through water

so

Baptism now saves you

that is

Baptism is not a removal of dirt

but

Baptism is an appeal to God

Insights:

This passage fits perfectly within Peter's overall aim to encourage believers facing such trials and persecution that they are in danger of losing hope that God cares for them or will fulfill his salvation promises. Peter has already affirmed that suffering is not only not a sign that God has removed his caring hand, but is in fact a means God uses to bring about greater glory and blessing. He has also presented Christ as an example of godly suffering (a point he will come back to in ch.4). Now Christ's sufferings are shown to be the means by which he vanquishes his enemies and brings his people to God - a reality that those who put their hope in God can take courage in and be assured that their union with Christ is secure.