<span>The very nature of chemistry presents us with a tension. A tension between the exhilaration of diversity of substances and forms on the one hand and the safety of fundamental unity on the other. Even just the recent history of chemistry has been al1 about this tension, from the debates about Prout's hypothesis as to whether there is a primary matter in the 19th century to the more recent speculations as to whether computers will enable us to virtually dispense with experimental chemistry.</span>