(see my post A Question of Identity)
Rebecca Solnit illustrates this point well in the chapter on urban walking in her book Wanderlust where she compares it to "a sort of basking in solitude". Being alone in the country outside of any human contact is quite different to being alone in the city, where you are alone amongst strangers and she maintains that it is one of life's starkest of luxuries to be "a stranger surrounded by strangers, to walk along silently bearing one's secrets and imagining those of the people one passes".
This theme is also touched upon in a book I am currently reading London Fragments - A Literary Expedition by Rüdiger Görner - a collection of essays exploring the capital's literary landscape from the point of view of the outsider, the non-Londoner. In a chapter about the London inhabited by European exiles, a quote from the novel 'Die Unsichtbare Wand' (The Invisible Wall) by the writer and scholar H G Adler, sums up the way in which London seems to suck in and find room for all its inhabitants:
"Let me disappear in the cosmopolitan city. It is incalculable, confused, eerie... it has mysterious neutrality....You cannot belong to this city, yet you are in it, independent, almost free, you are little touched by it and everyone minds their own business. I can foresee that I will never be completely lost specifically because of its forlornness."This forlornness is sometimes quite palpable in certain areas and seems to be the default mood of the city - a kind of melancholy which haunts the streets despite the crowds and the noise, where each one of us is alone with our thoughts yet part of the fabric of the streets.
However, things have changed since these words were written and it is probably true to say that nowadays you are never truly alone in the city. Wherever you go, just look up and you will see the ubiquitous security camera with its all-seeing eye trained on you. At least they can't read your thoughts......yet.