Is rising inequality the sickness that could yet kill capitalism? It's a debate currently raging in politics as well as economics. President Obama says income inequality is the defining challenge of our time. The influential American economist Deirdre McCloskey thinks that is to misunderstand 300 years of global growth and enrichment. She focuses on the enduring power of innovation, rather than wealth distribution. So is it ok for the rich to enjoy a party to which no one else is invited?(Photo: American economist Deirdre McCloskey)