It is written, “Behold, how good and how pleasant it is for brethren to dwell together in unity.” (Psalm 133) Where there is unity there is peace and development. But unity cannot be achieved unless people know themselves by nature. For this reason, this book has been written to make people aware of the different kinds of human nature in order to make right choices in marriage, friendship, and leadership, as well as in careers, professions, and occupations. This book will also enable people to know peace: a medicine that serves as the source of unity and development in life and society, and that helps nations, as a whole, to prevail. The Bible says, “My people are destroyed for lack of knowledge.” This book is full of divine truth. Hear it to be wiser.