Berthold Gunster is the founder of the Omdenken, or Flip Thinking, philosophy. After studying at the Theatre Academy in Utrecht he worked as a theatre director and writer for years. Since 2001 he and his team have been offering trainings, workshops and shows about Omdenken to companies and individuals. Berthold has written thirteen bestsellers about the Omdenken theory. Flip Thinking beautifully illustrates how a person who can turn a negative into a positive can never be defeated. The book is available now in shops and online.