"Principles of Universal Unity" is a book written by the great spiritual leader `Abdu'l-Bahá, who preached peace, tolerance and unity among the people of the whole world. In this book, the author reveals important principles and ideas necessary to achieve harmony and coexistence of all peoples on the planet. It calls for mutual understanding, deep trust and respect for other cultures and religions. This book is an important source of inspiration for those who seek to build a unified and harmonious world where peace and love reign.