In "Romeo and Juliet, what philiosophical observations does Friar Lawrence make in Act 2, Scene 3?

There are three basic philosophies that Friar Laurence expresses in this scene, and all have to do with his Fransican background.   

As a Fransican, he is dedicated to the care of the soul and his task is to advise pentintents of the ways in which their lives may go off course.  Thus, when he rightly (according to doctrine) says,  "Virtue itself turns vice being misapplied , / And vices sometime's by action dignified," he is expressing care for Romeo's soul, in that he urges the young man to examine his actions and see where truth lies. 

Secondly, he acts as a confessor, a confidant that Romeo can tell his sins to and expect to be forgiven and guided.  "God pardon sin," he tells Romeo (2.3.41).  Then, he urges Romeo to "Be plain, good son, and homely in thy drift; /  Riddling confession finds but riddling shrift, " (2.3.51-52). 

Lastly, Fransiscan philosophy dictated that wordly ornamentation led to corruption of the soul; so while Friar Laurence here is not speaking directly of Romeo's attire, he is urging him to cast off justifications for his behavior.  He can only expect good advice if he comes to the priest morally "naked." 

Of course, we see that the Friar himself is not following his own dictates, but that is for another post.