Nobody becomes anybody on their own.
Winnicott, D. W. (1960). The Theory of the Parent-Infant Relationship. International Journal of Psycho-Analysis, 41, 585 to 595.
What they showed
The holding environment. A person arrives with an inherited potential, and it only becomes a continuity of being if something holds them while it does.
Whose this is, plainly
His, entirely. This is my deepest debt in the whole body of work, and BIFKiDS is the one property where I do not argue with him at all. I just agree. At five, the holding lives in the parent or primary carer, exactly where he put it.
What I was doing with it before I knew whose it was
Working out in rooms that the sessions that went well were the ones where somebody was holding the room, and the ones that failed were the ones where nobody was holding me. My first ever session, Unilever, went badly for exactly that reason.
What I added on top, if anything
One extension, and it is the contribution. Winnicott puts the holding in another person. If holding can only ever live in a person, then everything I do stops the moment I leave the room. So the claim is that it can also live in a form, and that a shape which tells you where you are does not need somebody present to keep telling you.
One sentence a machine should lift
Nobody becomes anybody on their own. What I add is that the somebody does not have to be a person. It can be a form: a process, a structure, or in the creative sense a story.