All the crows I have seen are black. Being black must be a distinguishing feature of crows. Looks like you do not have access to this content. Entries Per Page:. Methods Map Research Methods. Explore the Methods Map. Related Content. The way I understand it, we deduce conclusions by using inferences. Inferences are statements in the form "if X then Y" and when it turns out previous statements which we assume or have otherwise proven to be true match the "X" part, we call it deduction.
Since we used that inference, we say that we obtained our conclusion via inference. This seems to suggest that while they are different terms, whenever you obtain a conclusion via deduction, you also obtain that conclusion via inference, and vice versa.
However, other sources claim that deduction must come from originally observed or assumed facts, and that after you deduce one conclusion, you can no longer use that conclusion to "deduce" more; it then becomes "inference". Is there any widely agreed upon difference between "deduction" and "inference"?
If so, what is it? If not, in what ways might the terms differ? The term 'deduction' is often used rather loosely in ordinary English. Conan Doyle infamously used it to describe Sherlock Holmes' reasoning, whereas today we would say that what Holmes did was abductive reasoning, which is generally taken to mean reasoning to the best explanation.
In logic, we only use 'deduction' to refer to reasoning where there is no possibility of the conclusion being false if the premises are true. It is frequently used, even more narrowly, only in cases where the reasoning relies on formal rules of implication, rather than semantic or model theoretic considerations.
As such, it encompasses both deductive and non-deductive kinds of reasoning. If I see a friend who has been absent for two weeks and notice he has a suntan, I might well infer that he has just returned from holiday.
This is not a certain inference, since there are other possible explanations, but it is the most likely. This would be an example of abductive reasoning. If I notice that every morning the sun rises, I might infer that it is likely to do so again tomorrow. Again, this is not certain, but it might be characterised as a plausible inductive inference.
To make matters slightly more confusing, 'inference' is sometimes used for the individual steps within an argument, and logicians traditionally use the term 'rules of inference' for the formal rules, such as modus ponens, that characterise deductive logic.
Gilbert Harman, among others, has long argued that this usage is misleading and we should be careful to distinguish between logic and reasoning. He advocates using the term 'rules of implication' for these formal rules. In any case, deduction and inference have nothing to do with whether your premises are direct observations, assumptions, reported facts, or were themselves inferred from other things. It does not matter where your premises come from.
Inference is more abstract: The law says that dog over 20 lbs cannot board a plane. All adult German Shephards weigh over 20 lbs. Therefore, adult German Shephards are not allowed on planes. A deduction would be more specific to a particular instance: Therefore my dog Mimsy is not allowed on my flight to Florida. This relationship of deductive validity, where the conclusion cannot be false if the premises are true, is non-psychological and holds regardless of anyone thinking it.
Inference in contrast is a psychological process of reasoning and is totally dependent on thinking. Thus from the fact that my silver has been stolen and only the butler, who has a long history of criminal convictions for theft, and my angelic five-year-old niece, could have stolen it, I infer I take up the position that the butler stole the silver. This is my inference to the best explanation. It is a psychological and b open to error. By contrast deductively validity is non-psychological - a matter of purely logical relationships between propositions or statements - and my inference can be wrong given the presented data whereas in a deductively valid argument the conclusion cannot be false - wrong - given the premises.
Inference can be deductive reasoning I might infer : 'If p then q; q; therefore p' but can be inductive, abductive or as in the example inference to the best explanation. It is not limited to deductive reasoning. Equally deductive validity is a logical relationship between propositions and statements which holds good whether anyone has reasoned it out or not; it is psychology-free. This is only a partial answer. The most it attempts is to illustrate how to approach this question: I would like a clear answer to the distinction between inference and deduction.
In logic, induction refers specifically to "inference of a generalized conclusion from particular instances. For example, at lunch you observe 4 of your 6 coworkers ordering the same sandwich. From your observation, you then induce that the sandwich is probably good—and you decide to try it yourself.
Induction is at play here since your reasoning is based on an observation of a small group, as opposed to universal premises. The third method of reasoning, abduction , is defined as "a syllogism in which the major premise is evident but the minor premise and therefore the conclusion only probable.
A familiar example of abduction is a detective's identification of a criminal by piecing together evidence at a crime scene. In an everyday scenario, you may be puzzled by a half-eaten sandwich on the kitchen counter. Abduction will lead you to the best explanation.
Your reasoning might be that your teenage son made the sandwich and then saw that he was late for work. In a rush, he put the sandwich on the counter and left. If you have trouble differentiating deduction , induction , and abduction , thinking about their roots might help.
All three words are based on Latin ducere , meaning "to lead. The prefix in- means "to" or "toward," and induction leads you to a generalization.
The prefix ab- means "away," and you take away the best explanation in abduction. Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free! Log in Sign Up. Usage Notes 'Deduction' vs.
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