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.

The only real progress lies in learning to be wrong all alone.

All men's misfortunes spring from their hatred of being alone.

When so many are lonely as seem to be lonely, it would be inexcusably selfish to be lonely alone.

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

All of our unhappiness comes from our inability to be alone.

I paint self-portraits because I am so often alone, because I am the person I know best.

Living alone makes it harder to find someone to blame.

Always give a word or sign of salute when meeting or passing a friend, or even a stranger, if in a lonely place.

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