As a science, logic institutes an analysis of the process of the mind in reasoning, and investigating the principles on which argumentation is conducted; as an art, it furnishes such rules as may be derived from those principles, for guarding against erroneous deductions. Some are disposed to view logic as a peculiar method of reasoning, and not as it is, a method of unfolding and analysing our reason. They have, in short, considered logic as an art of reasoning. The logician's object being, not to lay down principles by which one may reason, but by which all must reason, even though they are not distinctly aware of them - to lay down rules not which may be followed with advantage, but which cannot possibly be deviated from in sound reasoning. [ R. Whately ]