Introduction:

Medieval: Much of Dante's work illustrates medieval beliefs, especially the otherworldy outlook that considers the next world to be all important & this world to be significant only in so far as it decides where we will spend eternity.  He also has a medieval & static notion of economics & a religious scale of values that considers blasphemy or other imagined crimes against God to be much worse than murder or rape or some other such horrific act.  Dante's work can also be seen as the first glimmer of Renaissance values.  A loyal Catholic, there is nonetheless something disturbing about finding so many of the clergy in hell.  More telling is Dante's assumption that he (rather than the church) knows the mysterious of the next world.  True, these may be speculations & imaginative illustrations, but what Dante does in presenting a unified narrative tacitly claims an authority far different from that arising from the usual practice of quoting scripture & explicating it.

You Get What You Want: Dante's God evidently enjoys irony.  Dante's idea is that people spend much of their lives dedicated to some vice that they literally sell their soul to obtain.  So it is poetic justice to have them "enjoy" an eternity of what they thought they couldn't live without.  Adulterous lovers spend eternity in each other's company.  Flatters, whose mouths spewed nothing but excrement, find themselves eternally buried in it.  The point is that you need to think very hard about what you want.  Obviously, Dante suggests that we all want heaven.  Consequently, we need to be self-consciously dedicated to this goal 24 hours a day.

Natural Law: The early church borrowed this idea from Stoic philosophy.  The idea is that God directly created nature.  Therefore natural sequences or processes are not accidental or neutral.  They were put into operation by God Himself.  Any attempt to thwart the working or the results of natural processes, or even attempts to evade natural processes, are sins.  At one time, getting vaccinated in order to prevent disease was condemned as sinful, because it was seen as an attempt to evade the plans that God had for you.  We are more familiar with the Vatican's opposition to birth control on the grounds that it violates natural law.  The idea is that sex produces babies.  Contraception prevents this natural outcome & is consequently sinful.  Dante appeals to natural law arguments in several places, e.g., when he talks about "natural" economic processes:
11.109    the usurer takes another way,
              he scorns Nature in itself
 

Click on the next section: Background above.