How we cite our quotes: (Act.Scene.Line)
Quote #4
Why didst not thou pity her? What an excellent
Honest man might'st thou have been
If thou hadst borne her to some sanctuary
Or bold in a good cause, opposed thyself
With thy advanced sword above thy head
Between her innocence and my revenge! (4.2.263-68)
After he's carried out Ferdinand's orders to murder the Duchess, Bosola finds out that Ferdinand has no intention of rewarding him. Ferdinand tells Bosola that he's the real bad guy for following Ferdinand's orders, and should have protected the Duchesses from him. This basically the total reversal of the "gratitude" that Bosola thinks of as binding him to Ferdinand in the first place; he's not going to reward Bosola for his service, and in fact refutes the very terms of their relationship.
Quote #5
Your brother and yourself are worthy men,
You have a pair of hearts are hollow graves,
Rotten, and rotting others; and your vengeance,
Like to chained bullets, still goes arm in arm.
You may be brothers: for treason, like the plague,
Doth take much in a blood. I stand like one
That long hath ta'en a sweet and golden dream:
I am angry with myself now that I wake. (4.2.308-14)
Here's the moment where Bosola shakes off the chains of service to Ferdinand. Bosola voicing his less-than-flattering opinion of the Aragonian brothers is nothing new, but it's interesting to hear him characterize his service to them as "a sweet and golden dream." He's hated these guys all along, but his hopes for a rewarding relationship with them has kept him "asleep," and allowed him to ignore his own morality.
Quote #6
[…] whilst a guilty conscience
is a black register wherein is writ
all our good deeds and bad, a perspective
that shows us hell […] (4.2. 346-49)
The Duchess has revived for a moment only to, darn it, die again, this time permanently. Bosola, now regretting his actions, describes his own conscience (which, Breaking News, he does indeed have) as a record of all of his actions, which also acts as a mirror that shows hell. It's worth mentioning that this is a really determined view of ethics. You do a thing, it's either a good or a bad thing, and depending on which you will see hell or something else. How does this compare with the way Bosola feels about morality by the very end of the play?