Transitional Space
Transitional space is D. W. Winnicott's name for the intermediate zone between inner fantasy and outer reality, first seen in a child's blanket or teddy and later extended to play, art and culture. Nobody asks whether the teddy was found or invented, and that suspension is the point. Children's attachment to comfort objects is well documented and varies strongly across cultures and sleeping arrangements. The broader claim, that this space is the root of creativity and of culture, is theoretical and untested.
What it is
Winnicott presented the paper on transitional objects and transitional phenomena in 1951 and published it in the International Journal of Psychoanalysis in 1953. Playing and Reality, in 1971, extends the idea into what he called potential space, the area of experiencing that lies between the individual's inner world and shared external reality, and in which play and cultural life take place.
The everyday form is easy to recognise. A toddler will not sleep without a particular frayed blanket, which is neither simply a thing in the world nor simply part of her. Adults keep versions of the same space in hobbies, rituals and workshops, and some brands sell a small piece of it, in the particular mug that makes the morning feel safe.