It is shown that any combinational function can be implemented by a multiplexer of appropriate width. Since these logic elements can also perform sequential operations, entire digital systems can be implemented with multiplexers. Such systems are of particular relevance to optical implementations as multiplexers using liquid crystal electro-optic elements can be realised. The large number of pixels available on a single display leads to the concept of significant optical systems implemented using two-dimensional arrays of uncommitted multiplexers. Since the multiplexer width is critical in determining the system efficiency, the implementation of commonly occurring logic functions is presented to determine the optimum width.