Everyone is exposed to manipulation daily, and everyone manipulates too. The impact of manipulations in personal, social, and political life is enormous. Is this tragic? Is it avoidable? Is it always morally bad or regrettable? To answer these questions, we need a theory of manipulation. This book is the first comprehensive philosophical theory of manipulation. Shlomo Cohen offers a new theory on what manipulation is, distinguishing it from other kinds of influence, and assesses the basic moral status of manipulation. In contrast to prevailing views, he argues that manipulation, though often morally bad, is not inherently morally bad, and that alongside its dangers, it has a central role as a 'lubricant' of social frictions which helps to regulate social and political relations. His analysis offers a window to better understanding the ethics of the interplay of reason and power in human relations.