“Theatre is a form of knowledge; it should and can also be a means of transforming society. Theatre can help us build our future, rather than just waiting for it.”
This quote comes from the preface to the first edition on page xxxi, published in 1992 by Routledge. In the second edition published in 2002, as listed here, the quote can be found on page 16.
Augusto Boal is a Brazilian who focused on drama theory, political activism, and theater. He is well known for his book "Theater of the Oppressed" and refers to using theater to promote social and political change.