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Ian Watt:
"The greatness of Descartes was primarily one of method, of the a thoroughness 
  of his determination to accept nothing on trust; and 1- his Discourse on Method 
  ( 1637) and his Meditations did much to bring about the modern assumption whereby 
  the pursuit of truth is conceived of as a wholly individual matter, logically 
  independent of the tradition of past thought, and indeed as more likely to be 
  arrived at 
  by a departure from it. 
The novel is the form of literature which most fully reflects this individualist 
  and innovating reorientation. Previous literary forms had reflected the general 
  tendency of their cultures to make conformity to traditional practice the major 
  test of truth: the plots of a classical and renaissance epic, for example, were 
  based on past history or fable, and the merits of the author's treatment were 
  judged largely according to a view of literary decorum derived from the accepted 
  models in the genre. This literary traditionalism was first and most fully challenged 
  by the novel, whose primary criterion was truth to individual experience - individual 
  experience which is always unique and therefore new. The novel is thus the logical 
  literary vehicle of a culture which, in the last few centuries, has set an unprecedented 
  value on originality, on the novel; and it is there-fore well named."
...
"When Defoe … began to write fiction he took little notice of the dominant 
  critical theory of the day, which still inclined to wards the use of traditional 
  plots; instead he merely allowed his narrative order to flow spontaneously from 
  his own sense of what his protagonists might plausibly do next. In doing so 
  Defoe initiated an important new tendency in fiction: his total subordination 
  of the plot to the pattern of the autobiographical memoire is as defiant as 
  assertion of the primacy of individual experience in the novel as Descartes's 
  cogito ergo sum was in philosophy."
Ian Watt, The Rise of the Novel, Peregrine, 1956, p. 13, 15