Few business topics have aroused more skepticism in recent years than the notion of corporate purpose, and for good reason. Too many companies deploy purpose as a promotional vehicle to make themselves feel virtuous and to look good to the outside world. Some have only foggy ideas about what purpose is and conflate it with strategy and other concepts like 'mission', 'vision' and 'values'. Even well-intentioned leaders don't understand purpose's full potential and engage with it half-heartedly and superficially. Having conducted extensive field research and interviewed leadership at purpose-oriented companies including Etsy, Lego and Microsoft, Ranjay Gulati reveals the fatal mistakes leaders unwittingly make when attempting to implement a reason for being. Moreover, he shows how companies can embed purpose much more deeply, delivering impressive performance benefits that reward customers, suppliers, employees, shareholders and communities alike. To get this right, leaders must fundamentally change not only how they execute purpose but also how they conceive of and relate to it. They must practice what Gulati calls deep purpose, furthering each organisation's reason for being more intensely, thoughtfully and comprehensively than ever before. As he argues, a deeper engagement with purpose can serve as a radically new operating system, enhancing performance while also delivering meaningful benefits to society. It's the kind of inspired thinking that businesses - and the rest of us - urgently need.