A saint is a person who practices the keystone human virtue of humility. Humility in the face of wealth and plenty, humility in the face of hatred and violence, humility in the face of strength, humility in the face of your own genius or lack of it, humility in the face of another's humility, humility in the face of love and beauty, humility in the face of pain and death. Saints are driven to humbling themselves before all the splendor and horror of the world because they perceive there to be something divine in it pulsing and alive beneath the hard dead surface of material things -- greater and purer than they are.
A hermit must have a deep experience of communion with humanity. Without this, you cannot be a hermit, because you would only be lonely. You would not be really solitary. To be alone and cut off from others would make you very unhappy, but to be alone, and to be deeply united with others, in deep communion, that is a possibility for which many people long. That is what I call solitude—over and against loneliness.