There are three stages of inquiry, demanding as many different kinds of reasoning governed by different principles. They are,
1, Retroduction, forming an explanatory hypothesis[;]
2, Deduction, tracing out the consequences that would ensue upon the truth or falsity of that hypothesis; and
3, Induction, the experimental testing of the hypothesis by inquiring whether its consequences are born out by fact, or not.
The recommendations of an explanatory hypothesis are
1st, verifiability; 2nd, simplicity; 3rd, economy.