McLuhan regularly invoked the mosaic as displaying the sort of coherence which he took to be the form of reality itself — and therefore of that type of human awareness most fitting to it.¹ Famously, he does so at the beginning of The Gutenberg Galaxy:

The Gutenberg Galaxy develops a mosaic or field approach to its problems. Such a mosaic image of numerous data and quotations in evidence offers the only practical means of revealing causal operations in history. The alternative procedure would be to offer a series of views of fixed relationships in pictorial space. Thus the galaxy or constellation of events upon which the present study concentrates is itself a mosaic of perpetually interacting forms that have undergone kaleidoscopic transformation — particularly in our own time.

Like much else, this image was given to McLuhan for his further reflection by Sigfried Giedion in ‘A Faculty of Interrelations‘ from 1942:

In line with the whole structure of present-day knowledge we have to continue to train specialists. We do not want to educate dilettanti. There should be no popular courses on astronomy, on painting, on physics, literature, or ethnology. Rather should there be given an insight Into the methods and the interrelations of present-day knowledge [as practiced across all these fields by their best representatives]. In this way the mind of the coming specialist may be trained so that he will be able to conceive his own problems in relation to the whole. To make order, as I said at the beginning, is the first step towards a new universal. According to the structure of our period, the renascent universality has to be built up gradually. Like a mosaic, it has to be put together, piece by piece, by specialists of the new type. 

 The Gutenberg Galaxy was published twenty years later, in 1962.