In order to answer this question, I will first need to discuss what the Enlightenment ideals were and how they appear throughout Bach's sons" keyboard music. Infact the Enlightenment was a philisophical movement in the 18th century which attempted to raise standards of intelligence and education. In religion, personal beliefs rather than institutes such as the Church were encouraged. In Science the dismissal of superstition and anything without proof were preferred in favour of the study of the human mind and emotions. In politics prejudism and class systems were being challenged. .
As a consequence of all the new philosophies, this led to a change in the arts. The enlightenment encouraged naturalness and emotions, in drama this leads to more simplistic, serious dramas with a retreat from the supernatural plots to much more common natural scenarios.
In terms of the Enlightenment's affects on the music of the time; Barford suggests that "The concept of Enlightenment permits a more sophisticated view, when applied to music it cannot simply be reduced to the ideal of simplicity and naturalness- .
Grout however, disagrees:.
What people in the mid- and later eighteenth century wanted, according to its leading critics might be described as follows: the language of music should be universal, that is, not limited by national boundaries; music should be noble as well as entertaining; it should be expressive within the bounds of decorum; and it should be "natural" - free of needless technical complications and capable of immediately pleasing any sensitive listener. .
For some time the modern and old-fashioned styles co-existed alongside each other and the period of complete transition was slow. For example C.P.E Bach was writing music in the Empfindsamkeit style, while his father at the same time was writing his B-Minor mass. Classical composers criticised the old style for being too intellectual and mathematical e.