Loneliness

Wisdom from the screenplay of Thin Red Line:

Witt: Do you ever feel lonely?
Welsh: Only around people.

Of course it is otherness that provokes loneliness: it is the presence of other people (for example, people who don't know us or care about us) or the thought of other people -- these are what make us feel lonely. Loneliness is dissolved equally well by being surrounded by people who care about us; or by a perfection of solitude.