create the mental sound movie which we call reading.

The most definitive work we have on the phonetic letters 
is The Alphabet  by David Diringer. He begins his story as follows 
(p. 37):

          The alphabet is the last, the most highly developed, 
     the most convenient and the most easily adaptable 
     system of writing. Alphabetic writing is now universally 
     employed by civilized peoples; its use is acquired in 
     childhood with ease. There is an enormous advantage, 
     obviously, in the use of letters which represent single 
     sounds rather than ideas or syllables; no sinologist knows 
     all the 80,000 or so Chinese symbols, but it is also far 
     from easy to master the 9,000 or so symbols actually 
     employed by Chinese scholars. How far simpler is it to use