Question

What is Aragons logic behind selecting the silver casket?

Answer 1

Choice of Prince of Morocco's is straightforward. He firstly, chose the gold casket because it seemed the most obvious and most enviable choice.  

On the other hand, Arragon rejects lead casket because of the ominous caution, and thinks that gold refers to the silly populace.

Instead he chooses silver which indicates he will collect what he deserves.