On the fifth Tuesday, what did Morrie say is the foundation of everything?

From the text:

“The fact is, there is no foundation, no secure ground, upon which people may stand today if it isn’t the family. It’s become quite clear to me as I’ve been sick. If you don't have the support and love and caring and concern that you get from a family, you don’t have much at all. Love is so supremely important. As our great poet Auden said, ‘Love
each other or perish.’”