The nature of bonds between atoms is of fundamental importance to chemistry, since that science is to a large degree a study of the alteration of such bonds. Yet the inadequacy of bond diagrams in depicting important chemical compounds has been known from the very beginning of structural chemistry. Succeeding diagrammatic systems were discarded because of the failure of each system to account for certain phenomena. The ancient contest between idealism and materialism entered the discussion when chemists began using models that seemed physically inconceivable to some other chemists.
The formulas and models constructed by chemists must explain not only the composition of chemical compounds, but also their properties. In the first half of the nineteenth century no single convention or method of representing compounds was accepted. J. R. Partington remarked, "It was apparently considered a sign of independence of thought for every chemist to have his own set of formulae."1 As late as 1861 Friedrich August Kekulé gave nineteen different formulas for aceic acid.2
The reason for the fragmentation of theories and the use of multiple formulas lay in the inability of chemists to observe or measure molecules directly. Chemistry in general, and organic chemistry in particular, were frighteningly unknown. In 1835 Wöhler wrote to Berzelius, "organic chemistry appears to me like a primeval forest of the tropics, full of the most remarkable things."3 During the next thirty years chemists collected an astonishing amount of data and isolated many