The Commens Dictionary
Quote from ‘A Neglected Argument for the Reality of God (G)’
… Another question to be noted for later consideration is whether this first step in inquiry can conclude, if it can be called “concluding,” otherwise than in the interrogative mood, if grammarians will acknowledge such a mood. Certain it is that if a series of experience does no more than suggest an idea interrogatively, the mere occurrence of the suggestion, warrants us in regarding the movement of thought as having the essential character of this first stage of inquiry. I call this mode of inference, or, if you please, this step toward inference, in which an explanatory hypothesis is first suggested, by the name of retroduction, since it regresses from a consequent to a hypothetical antecedent. But while this explains why I have selected the vocable ‘retroduction’ to express my meaning, I claim the right, as inventor of the term, to make its definition to be, the passage of thought from experiencing something, E, to predicating a concept of the mind’s creating; the subject of the predication being a specified class to which E belongs, or an indefinite part of such class.
The second stage of inquiry consists in deducing the consequences of the retroductive hypothesis. The word “retroductive,” however, is surplusage; for every hypothesis, however arbitrary, is suggested by something observed, whether externally or internally and such suggestion is, from a purely logical point of view, retroduction.