Paul Thomas Anderson, despite the seeming variety of his filmography, only really makes movies about a few things: lost souls, the search for meaning or purpose in life, and the struggle for/against family.
In Boogie Nights the lost soul is Eddie Adams and he is searching for his value, his place in the world, all while struggling against who his parents, particularly his mother, think he is and thus should be, and who he actually wants to be; it’s a search and struggle that lead him into the embrace of an unconventional but accepting new family, that of Jack Horner’s porn enclave.
In Magnolia pretty much the entire cast is made up of lost souls searching for connection, redemption, and/or acceptance from families of blood, circumstance, and their own forging.
In Punch-Drunk Love Barry is perpetually lost in his own person and the image others have of him, and also perpetually searching for a lifeline out of his prescribed existence which is constantly and demeaningly reinforced by his gaggle of overbearing sisters.
I could keep going through the remainder of PTA’s films, but a) you get the point – Anderson makes films about people intent, sometimes fatally so, on finding their purpose in life – and b) the latest and perhaps greatest video essay to-date from Jack’s Movie Reviews does it better than I ever could. His analysis not only eruditely explains the characters who inhabit Anderson’s oeuvre, it also presents their respective dilemmas as uniquely American, a sort of botched manifest destiny of the soul.
There are literally dozens of videos about Anderson and his work out there, I’ve even made one myself, but JMR’s is top 1%, which makes it not only must-see, but indispensable to your education of the director.