  We present a discussion of the design issues and trade-offs that have been
considered in putting together a new concept for MOSAIC, the multi-object
spectrograph for the E-ELT. MOSAIC aims to address the combined science cases
for E-ELT MOS that arose from the earlier studies of the multi-object and
multi-adaptive optics instruments. MOSAIC combines the advantages of a
highly-multiplexed instrument targeting single-point objects with one which has
a more modest multiplex but can spatially resolve a source with high resolution
(IFU). These will span across two wavebands: visible and near-infrared.
