This discussion explores the significance of Section 66 of the Evidence Act in civil lawsuits, particularly concerning secondary evidence. It clarifies that if a party requests original documents under Order 11 Rules 12 and 14 of the CPC, and the other side refuses, the requesting party may apply for secondary evidence under Section 65. The necessity and implications of providing notice under Section 66 are also examined, along with the court's discretion in allowing such evidence.