Pete wrote at the time:

We miss him already but his love of life, and his moral passion, will stay with us forever...We are left with memories of his powerful intellect, his extensive legacy, his personal warmth and his deeply felt love for Mom, me, and all those close to him.

So what was this "moral passion" of Pete's father?

It was a passion for Marxism and more specifically the philosophy of  Antonio Gramsci.

Joseph, who was a professor at Notre Dame, co-translated and co-edited the three-volume English edition of Antonio Gramsci's Prison Notebooks. He also was a founding member and president of the International Gramsci Society.

Who was Gramsci?