The Pillars of the Earth (Kingsbridge, #1)

by Ken Follett

He was now a year and half old, and his current obsession was putting things into other things. He had four or five kitchen bowls in front of him, and he tirelessly put the smaller ones inside the larger and tried to put the larger inside the smaller. Jack was very struck by the idea that Tommy did not know instinctively that a large bowl would not fit inside a small one; that this was something human beings had to learn.