Show Deductive, Inductive and Abductive ReasoningTIP Sheet Reasoning is the process of using existing knowledge to draw conclusions, make predictions, or construct explanations. Three methods of reasoning are the deductive, inductive, and abductive approaches. Deductive reasoning: conclusion guaranteed If x = 4 In this example, it is a logical necessity that 2x + y equals 9; 2x + y must equal 9. As a matter of fact, formal, symbolic logic uses a language that looks rather like the math equality above, complete with its own operators and syntax. But a deductive syllogism (think of it as a plain-English version of a math equality) can be expressed in ordinary language: If entropy (disorder) in a system will increase unless energy is expended, In the syllogism above, the first two statements, the propositions or premises, lead logically to the third statement, the conclusion. Here is another example: A medical technology ought to be funded if it has been used successfully to treat patients. A conclusion is sound (true) or unsound (false), depending on the truth of the original premises (for any premise may be true or false). At the same time, independent of the truth or falsity of the premises, the deductive inference itself (the process of "connecting the dots" from premise to conclusion) is either valid or invalid. The inferential process can be valid even if the premise is false: There is no such thing as drought in the West. In the example above, though the inferential process itself is valid, the conclusion is false because the premise, There is no such thing as drought in the West, is false. A syllogism yields a false conclusion if either of its propositions is false. A syllogism like this is particularly insidious because it looks so very logical–it is, in fact, logical. But whether in error or malice, if either of the propositions above is wrong, then a policy decision based upon it (California need never make plans to deal with a drought) probably would fail to serve the public interest. Assuming the propositions are sound, the rather stern logic of deductive reasoning can give you absolutely certain conclusions. However, deductive reasoning cannot really increase human knowledge (it is nonampliative) because the conclusions yielded by deductive reasoning are tautologies-statements that are contained within the premises and virtually self-evident. Therefore, while with deductive reasoning we can make observations and expand implications, we cannot make predictions about future or otherwise non-observed phenomena. Inductive reasoning: conclusion merely likely Conclusions reached by the inductive method are not logical necessities; no amount of inductive evidence guarantees the conclusion. This is because there is no way to know that all the possible evidence has been gathered, and that there exists no further bit of unobserved evidence that might invalidate my hypothesis. Thus, while the newspapers might report the conclusions of scientific research as absolutes, scientific literature itself uses more cautious language, the language of inductively reached, probable conclusions: What we have seen is the ability of these cells to feed the blood vessels of tumors and to heal the blood vessels surrounding wounds. The findings suggest that these adult stem cells may be an ideal source of cells for clinical therapy. For example, we can envision the use of these stem cells for therapies against cancer tumors [...].1 Because inductive conclusions are not logical necessities, inductive arguments are not simply true. Rather, they are cogent: that is, the evidence seems complete, relevant, and generally convincing, and the conclusion is therefore probably true. Nor are inductive arguments simply false; rather, they are not cogent. It is an important difference from deductive reasoning that, while inductive reasoning cannot yield an absolutely certain conclusion, it can actually increase human knowledge (it is ampliative). It can make predictions about future events or as-yet unobserved phenomena. For example, Albert Einstein observed the movement of a pocket compass when he was five years old and became fascinated with the idea that something invisible in the space around the compass needle was causing it to move. This observation, combined with additional observations (of moving trains, for example) and the results of logical and mathematical tools (deduction), resulted in a rule that fit his observations and could predict events that were as yet unobserved. Abductive reasoning: taking your best shot A medical diagnosis is an application of abductive reasoning: given this set of symptoms, what is the diagnosis that would best explain most of them? Likewise, when jurors hear evidence in a criminal case, they must consider whether the prosecution or the defense has the best explanation to cover all the points of evidence. While there may be no certainty about their verdict, since there may exist additional evidence that was not admitted in the case, they make their best guess based on what they know. While cogent inductive reasoning requires that the evidence that might shed light on the subject be fairly complete, whether positive or negative, abductive reasoning is characterized by lack of completeness, either in the evidence, or in the explanation, or both. A patient may be unconscious or fail to report every symptom, for example, resulting in incomplete evidence, or a doctor may arrive at a diagnosis that fails to explain several of the symptoms. Still, he must reach the best diagnosis he can. The abductive process can be creative, intuitive, even revolutionary.2 Einstein's work, for example, was not just inductive and deductive, but involved a creative leap of imagination and visualization that scarcely seemed warranted by the mere observation of moving trains and falling elevators. In fact, so much of Einstein's work was done as a "thought experiment" (for he never experimentally dropped elevators), that some of his peers discredited it as too fanciful. Nevertheless, he appears to have been right-until now his remarkable conclusions about space-time continue to be verified experientially. References 2. Thagard, Paul and Cameron Shelley. "Abductive reasoning: Logic, visual thinking, and coherence." Waterloo, Ontario: Philosophy Department, Univerisity of Waterloo, 1997. June 2, 2005. <
http://cogsci.uwaterloo.ca/Articles/Pages/%7FAbductive.html> What is the process of reaching a general conclusion by examining specific examples?Inductive reasoning begins with observations that are specific and limited in scope, and proceeds to a generalized conclusion that is likely, but not certain, in light of accumulated evidence. You could say that inductive reasoning moves from the specific to the general.
Is the process of reaching a general conclusion?Inductive Reasoning is the process of arriving at a general conclusion based on observations of specific examples.
What is deductive and inductive reasoning?Deductive reasoning, or deduction, is making an inference based on widely accepted facts or premises. If a beverage is defined as "drinkable through a straw," one could use deduction to determine soup to be a beverage. Inductive reasoning, or induction, is making an inference based on an observation, often of a sample.
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