-
Abduction
-
Deduction
-
Induction
This Youtube video distinguished and explained most clearly for me:
Understanding these 3 words’ etymologies can help:
Retroduction : The prefix “retro,” occurs in loanwords from Latin having to do with going backward. Yet, the prefix “retro” provides an implication of deliberateness–of deliberately “choosing” to go backward for a purpose. Thus “retroactive” means choosing to go back to an earlier date and make something operative as of that date. “Retrofit” means choosing to go back and modify an earlier model of something with an improvement of some sort. The combination of the prefix “retro” (as deliberately “going backward”) with the suffix “ductive” from the Latin ducere (to lead) places the meaning of retroduction as “deliberately leading backward.” This implies that retroduction is intended to be a deliberate and recursive process involving more than the making of an abductive inference. Its Latin roots indicate that “retroduction” refers, not only to the apprehension of a “surprising fact,” and an ensuing hunch, but also that the hunch, once formed, is deliberately and recursively taken “backward” for analysis and adjustment (requiring deduction and induction), before it is engendered into a hypothesis worthy of extensive testing.
Abduction : The prefix “ab” appears in loanwords from Latin where it meant “away from.” Thus we have words like “abdicate” and “abolition”–going “away from” the throne and from slavery, respectively. Thus, when the prefix “ab” (away from) is combined with the suffix “ductive” (from the Latin ducere, meaning to lead) we have the meaning of abduction as “leading away from.” The term “abduction” fits well with the concept of abduction as moving “away from” a particular course or topic, as one would when responding to an anomaly, or a “surprising fact.” The Latin root for “abduction” does not fit with the idea of going backward to explicate and evaluate an idea. Rather, this root indicates that the outward movement of an abductive inference allows the result of such an inference to be left as a completion, or used as the sole means for further exploration of possibilities–as in the arts.
Deduction : The prefix “de” from Latin loanwords refers to separation, removal, and negation. When we combine the prefix “de” (to separate) with the suffix “ductive” (to lead), we have the meaning of deduction as “leading to separation, removal, or negation,” which are the goals and consequences of deductive reasoning.
Induction : The prefix “in,” also from the Latin has to do with inclusion. Thus, the prefix “in” (to include) combined with the suffix “ductive” means “leading into” (or including), as one would do when reaching a conclusion by estimating from a sample, or generalizing from a number of instances. Therefore, based upon their Latin derivations (to which Peirce was partial, as he was for Greek roots) our four terms have the following meanings:
Retroduction = deliberately leading backward.
Abduction = leading away from
Deduction = leading to separation, removal, or negation.
Induction = “leading into” (or including) .Doug Spoonwood It’s not true that deduction will necessarily lead you from more general to less general statements. In fact, deduction can go from less general to more general statements. There’s an old paper by Lukasiewicz called “Remarks on Nicod’s Axiom and Generalizing Deduction”. In that paper he starts with a less general formula than Nicod’s and deduces Nicod’s formula. He only uses deduction. As perhaps a better example, there exists axiom sets (which could get combined into a single axiom) where (((p→0)→0)→p) is an axiom. But, the more general (((p→q)→0)→p) can get deduced.