Full Idea
Implication is cumulative, in a way that inference may not be. In argument one accumulates conclusions; things are always added, never subtracted. Reasoned revision, however, can subtract from one's view as well as add.
Gist of Idea
Implication just accumulates conclusions, but inference may also revise our views
Source
Gilbert Harman (Change in View: Principles of Reasoning [1986], 1)
Book Reference
Harman,Gilbert: 'Change in View: Principles of Reasoning' [MIP 1986], p.4
A Reaction
This has caught Harman's attention, I think (?), because he is looking for non-monotonic reasoning (i.e. revisable reasoning) within a classical framework. If revision is responding to evidence, the logic can remain conventional.