A series of Clark Lectures given at Trinity College, Cambridge, in the year after T. S. Eliot had delivered them, Aspects of the Novel (1927) was written after Forster had finished with novel writing. It is an idiosyncratic survey of fiction from Defoe to Joyce. The lectures were delivered between January and March 1927 and were less academic expositions than one author's perspective on literary history, style and form.
Forster's "Aspects of the Novel" was a pioneering work for several reasons, chief among them being it was the first time that someone had established the subtle difference between 'story' and 'plot.' Aristotle in his "Poetics" (3rd century B.C), remarked on the subtle difference between 'incident' and 'plot.' But it was Forster who developed this idea and established the difference between 'story' and 'plot.'
According to Aristotle, 'incidents' are the raw material and 'plot' is an abstract concept which refers to the organisation of the incindents in drama. The same incidents can be organised in different sequences and each different arrangement will result in different 'plots.'
According to Forster, the subtle difference between 'story' and 'plot' is that both 'story' and 'plot' refer to the organization of 'incidents'; but with a stirking difference: in a 'story' the incidents are organized subsequently,that is, one after another and linked by the conjunction 'and' whereas in a 'plot' the 'incidents' are linked consequently by cause and effect.
Forster illustrates his theory with an example which has now become a cliche:
Story: 'the king died and the queen died.'
Plot: 'the king died and the queen died because of grief.'
In a 'story' there is no cause and effect relationship between the two incidents and hence the connection between the different incidents is slight. On the contrary, the 'plot' is characterised by a tighter and firmer organization because the two incidents are linked causally.