Differences Between Inductive Reasoning and Deductive Reasoning: The two terms, ‘reasoning’ and ‘argument’ have the same import. Thus, they can be used interchangeably. An argument is a reason, a fact or statement used to support a proposition which is the conclusion. The general sense of argument conveys a verbal dispute, but it its academic sense, it is simply the process of reasoning. Reasoning is the deduction of inferences or interpretations from the premises and the abstract thoughts to a conclusion. Reasoning and argument are relevant to the logical process.
A logical process is a systematic thought pattern from which an argument flows. Reasoning or argument is the third and the last stage of logical process following simple apprehension and judgment. It is from the act of reasoning that a new and final proposition (which is the conclusion) is formed in a logical process, based on the available premises. In a logical reasoning, the premise is the body of the argument which forms the basis from which the conclusion is drawn. The premise is also known as the evidence for the conclusion. It is the premise that provides justification for the conclusion.
It follows therefore that every argument or reasoning comprises two parts namely; the premise or premises (which is also known as evidence, reasons, justification, ground or proposition), and the conclusion or the final proposition.
Two examples of argument or reasoning are known to the field of logic, they are; deductive reasoning and inductive reasoning. Both are methods employable by scientists in their research.
Meaning of Deductive Reasoning (Deduction)
The origin of deductive reasoning is traceable to the popular philosopher, Aristotle, hence the other name foe deductive reasoning which is Aristotlean logic. Deductive reasoning is the type of reasoning where justification or reason flows from a premise which is universal to a final proposition or conclusion. Thus, in a deductive argument, the conclusion is strictly drawn from the premise, and the premise suggests the conclusion.
Deductive reasoning derives its conclusion from the already stated universal knowledge and then applies it to a particular knowledge. Thus, deductive reasoning moves from a universal knowledge to a particular one.
Deductive reasoning applies mainly in general philosophy, formal logic and mathematics. In a deductive reasoning, there can be more than two propositions but certainly not less than tow propositions. A deductive argument that has two premises and a conclusion is known as syllogism.
Here is an example of a deductive reasoning:
FIRST PREMISE – All birds can fly
SECOND PREMISE – Pigeon is a bird
CONCLUSION – Therefore, pigeon can fly
FIRST PREMISE – All ladies are beautiful
SECOND PREMISE – Sandra is a lady
CONCLUSION – Therefore, Sandra is beautiful.
From the above examples, it is seen that the first premise provided a ground for the second premise, while the second premise led to the conclusion, and then the conclusion which is a particular knowledge reconnected to and reflected the first premise which is the universal knowledge. This buttresses the description that reasoning is a linkage or network of propositions related by logic and reasons. In a deductive reasoning, the conclusion is always certain.
Meaning of Inductive Reasoning (Induction)
Inductive reasoning is also known as the Baconian Method, following its founder’s name, Francis Bacon. Inductive reasoning is directly the opposite of deductive reasoning. While deductive reasoning flows from the universal to a particular knowledge, inductive reasoning flows from a particular knowledge to a universal one. Inductive reasoning is simply described as an inference.
In an inductive reasoning, the conclusion is not necessarily certain; it is in fact probable. Arrival at the conclusion of an inductive reasoning is usually by inference. Thus, the conclusion need not flow from the premise.
Here is an example of a deductive reasoning:
FIRST PREMISE – Jason completes 100 metre race is 3 minutes, he is tall
SECOND PREMISE – Mike completes 100 metre race in 3 minutes, he is tall
CONCLUSION – Thereore, all tall people will complete a 100 metre race in 3 minutes
FIRST PREMISE – Ojo bought his standing fan at ten thousand naira
SECOND PREMISE – Oko bought his standing fan at ten thousand naira
CONCLUSION – Therefore, all standing fan is sold at ten thousand naira.
From the examples above it is seen that the first premise is not a universal knowledge but particular instead. It is from the first and second premises that an inference (which is the conclusion) is drawn; an inference which is not necessarily true or correct.
Differences Between Inductive Reasoning and Deductive Reasoning
Here are clear differences between inductive reasoning and deductive reasoning.
1. The first clear difference is that while deductive reasoning flows from a general or universal knowledge to a specific or particular one, inductive reasoning does exactly the opposite. Thus, are the opposites of each other. In effect, the premise of a deductive reasoning is a general statement; it refers to the whole world, and from there it narrows it down to a specific person, and then draws its conclusion from there.
The conclusion which is the final proposition reflects to the first premise which is the universal statement. Whereas for an inductive reasoning, it does not refer to the whole world at first but rather refers to a specific person starting from its first premise.
It is from this specific person in the first premise that the second premise is suggested, and then a generalized conclusion follows. Thus, the scope of an inductive reasoning starts from a narrow region and expands to the whole world.
2. In a deductive reasoning, the final proposition always comes from the stated premise. Therefore, it does not come from outside the premise. On the other hand, an inductive reasoning does not necessarily draw its conclusion from the stated premises, although it does not neglect them entirely.
It rather goes outside the premises by making its final proposition wider than the premise. An inductive reasoning therefore infers its conclusion from a mere reoccurring factor.
3. Because inductive reasoning makes an inference, it is liable to be flawed. Its premises do not necessarily justify, give reason or provide a sufficient ground for its final proposition; it rather makes an unfounded conclusion which may be true or not.
In an inductive reasoning, its premises are not necessarily false, but they do not provide enough justification for the conclusion, although the conclusion may be true. Thus, it is highly probable. On the other hand, deductive reasoning does not infer, it rather deduced its conclusion from an existing universal fact stated in the premise, and then applies it to a particular setting.
4. Once the premise of a deductive reasoning is true, then the conclusion will be correct. This is because the conclusion flows strictly from the premises stated, of which once they are true, then the conclusion will be correct. Thus, it is only a false premise that can lead to an incorrect conclusion in a deductive reasoning.
On the other hand, the premise of an inductive reasoning may be true but it does not provide sufficient ground or reason for the conclusion to be correct. Of course the conclusion could be correct but it can be liable to be flawed. Inductive reasoning simply makes generalizations which are not always correct.
5. Deductive reasoning flows from up to down, that is, from the premise to the conclusion, whereas inductive reasoning flows from down to top, that is, from the conclusion to the premise.
6. Deductive reasoning makes a certain conclusion. Once the premises are stated, the conclusion becomes certain because it cannot emanate from anywhere else asides from what is contained in the premise.
On the other hand, inductive reasoning makes a probable conclusion which is drawn from outside the premise.
7. The arguments in a deductive reasoning may either be valid or invalid whereas in an inductive reasoning, the arguments may either be strong or weak.
Deductive and inductive reasoning regardless of their differences, are very useful and complementary in the academic field, scientific field and in our every day reasoning and activities.