Why does this act open with Polonius and Reynaldo? What does this tell us about Polonius's character, and what theme or motif does it introduce in the play?

The act opens up with Polonius and Reynaldo as Polonius is unraveling a new scheme that is stored in his unstable mind. The scheme is for Reynaldo to go to Paris in order to spy on Polonius' son, Laertes. In my opinion, I have a feeling that Polonius has an overprotective nature with his children and though it may seem that he is crossing the line just to check up on his son, it shows the caring and radiant character in Polonius. “By indirections find directions out” (ii.i.73).  When Polonius says this to Reynaldo it insinuates that this is all for the greater good. His mindset is in the right place, it just seems that his actions are not equivalent to the message that he is trying to send. Laertes seems like he was brought up by his father in a well-mannered environment even though he does not seem to have the best relationship with his father. On the contrary when one is sheltered to only one side of the world, when he/she is exposed to the other realm, one tends to completely immerse themselves into that other side, trying to make up for what they missed out on. People generally mistake Polonius' methods for overbearing, tedious, or even unnecessary, but that is where the theme of the play is introduced. I think the author wanted the audience to discern that there is more the Polonius than he is showing. People are not always what they are perceived to be, they tend to be a lot more genuine than they appear or more devious. One is more prone to hide behind a mask emotionally, until someone can peel off their fake persona, reveal their true identity, and give their true self, meaning.

The theme that is introduced into the play is:

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Appearance vs Reality