If it's true that our species is alone in the universe, then I'd have to say the universe aimed rather low and settled for very little.

Even in the presence of others he was completely alone.

A man content to go to heaven alone will never go to heaven.

There are places and moments in which one is so completely alone that one sees the world entire.

I love to be alone. I never found the companion that was so companionable as solitude.

Absolutely lonely people have few personal interactions of any kind.

I restore myself when I'm alone.

I don't want to be alone, I want to be left alone.

As I get older I'm more and more comfortable being alone.

Every man must do two things alone he must do his own believing and his own dying.