Student or Learner
What does "its" refer to here? [Is this a right question?]
And, how should I understand "when things are right"?
Now the reader is ready for the book. In it he will find a complicated account of the mechanisms of mental evolution. He will learn how approximate or partial assimilation of information somewhat foreign to a scheme leads, when things are right, to disequilibrium and to compensations that enlarges the system and result again in an equilibrated structure with its property of reversibility and its feeling of necessity.
Source: Terrance Brown, Forword. In Jean Piaget(1985), The equilibration of cognitive structures: The central problem of intellectual development. The University of Chicago Press. p. xi.