In the 20th century, the idea of solitude formed the centre of Hannah Arendt's thought. A German-Jewish émigré who fled Nazism and found refuge in the United States, Arendt spent much of her life studying the relationship between the individual and the polis. For her, freedom was tethered to both the private sphere - the vita contemplativa - and the public, political sphere - the vita activa. She understood that freedom entailed more than the human capacity to act spontaneously and creatively in public. It also entailed the capacity to think and to judge in private, where solitude empowers the individual to contemplate her actions and develop her conscience, to escape the cacophony of the crowd - to finally hear herself think.
Action without contemplation = fiasco.
Contemplation without action = despair!