Deductive, Inductive
Both words have their origins in the PIE root deuk (to lead) and Latin ducere (to lead).1
Deduce, deductive
Deduce is from Latin de- (down) + ducere = to lead down, to derive. The verb deduce comes to English in the early 15th century meaning to show, to prove, to demonstrate. The sense of deduce meaning to draw a conclusion from something already known is from the 1520s. The adjective deductive (deduction based on inference from accepted principles) is from the 1660s.
Induce, Inductive
Induce is from Latin in- (into, in upon) + ducere = inducer (to lead into, bring in, introduce, conduct; persuade; suppose, imagine). The verb induce (to lead by persuasions or other influences) comes to English in the late 14th century. Induce, meaning to bring about by any method, is from the early 15th century; meaning to infer by reasoning is from the 1560s. The use of induce in relation to electro-magnetic forces is from 1777.
The adjective inductive (bringing on, inducing) is from the early 15th century. Inductive, as a term used in logic, is from 1764.
The noun induction, from the late 14th century, meant advancement toward the grace of God, and later, meant the formal installation of a clergyman. Induction, in relation to electrical influence, is from 1801. Induction in relation to military service is from 1934 American English.
How are deductive reasoning and inductive reasoning different?
Deduction starts from a general principle in order to arrive at some individual fact. For example, if we know for a fact that A = B and that B = C, we can ‘deduce’ that A = C. Or, acute angles are less that 90o. This angle is 45o; therefore, it is an acute angle. The general principle is that the ‘premises’ or ‘facts’ need to be ‘true’ in terms of logic and evidence. The problem with deductive reasoning is that you can overgeneralize or end up with invalid assumptions; for example: here are two ‘true’ premises—all swans are white, and David is white. Therefore, David is a swan.
On the other hand, induction begins with known instances and facts and arrives at generalizations. For example, if we know that certain facts or premises seem to be related, we can construct a ‘hypothesis’; i.e., a generalization from certain facts. However, with a hypothesis, further research (e.g., gathering more supportive data and evidence) is necessary in order to confirm the ‘truth’ of the original hypothesis. In this sense, a hypothesis can become a ‘theory’ or an explanation of something if addition research supports it. For example, here are two premises or ‘facts’: my father lives in a senior’s home. He is happy. Does inductive reasoning suggest that all men living in senior’s homes are happy? No. It suggests a hypothesis that would need to be checked out.
In brief
Deduction is from the general to the specific; induction is from the specific to the general. “Induction starts with known instances and arrives at generalizations; deduction starts from a general principle and arrives at some individual fact”2. Deductive reasoning can be more sound if the premises are ‘true’. Premises in inductive reasoning may be true but may not be universally true; therefore, more research and reasoning would be required.3
1 PIE deuk and Latin ducere are also the origin of words such as: abduct, aqueduct, conducive, conduct, conductor, duct, duke, education, introduce, production, reduction, seduction, and others.
2 https://www.etymonline.com/search?q=induction
3 https://examples.yourdictionary.com/deductive-reasoning-examples.html
Deduce, deductive
Deduce is from Latin de- (down) + ducere = to lead down, to derive. The verb deduce comes to English in the early 15th century meaning to show, to prove, to demonstrate. The sense of deduce meaning to draw a conclusion from something already known is from the 1520s. The adjective deductive (deduction based on inference from accepted principles) is from the 1660s.
Induce, Inductive
Induce is from Latin in- (into, in upon) + ducere = inducer (to lead into, bring in, introduce, conduct; persuade; suppose, imagine). The verb induce (to lead by persuasions or other influences) comes to English in the late 14th century. Induce, meaning to bring about by any method, is from the early 15th century; meaning to infer by reasoning is from the 1560s. The use of induce in relation to electro-magnetic forces is from 1777.
The adjective inductive (bringing on, inducing) is from the early 15th century. Inductive, as a term used in logic, is from 1764.
The noun induction, from the late 14th century, meant advancement toward the grace of God, and later, meant the formal installation of a clergyman. Induction, in relation to electrical influence, is from 1801. Induction in relation to military service is from 1934 American English.
How are deductive reasoning and inductive reasoning different?
Deduction starts from a general principle in order to arrive at some individual fact. For example, if we know for a fact that A = B and that B = C, we can ‘deduce’ that A = C. Or, acute angles are less that 90o. This angle is 45o; therefore, it is an acute angle. The general principle is that the ‘premises’ or ‘facts’ need to be ‘true’ in terms of logic and evidence. The problem with deductive reasoning is that you can overgeneralize or end up with invalid assumptions; for example: here are two ‘true’ premises—all swans are white, and David is white. Therefore, David is a swan.
On the other hand, induction begins with known instances and facts and arrives at generalizations. For example, if we know that certain facts or premises seem to be related, we can construct a ‘hypothesis’; i.e., a generalization from certain facts. However, with a hypothesis, further research (e.g., gathering more supportive data and evidence) is necessary in order to confirm the ‘truth’ of the original hypothesis. In this sense, a hypothesis can become a ‘theory’ or an explanation of something if addition research supports it. For example, here are two premises or ‘facts’: my father lives in a senior’s home. He is happy. Does inductive reasoning suggest that all men living in senior’s homes are happy? No. It suggests a hypothesis that would need to be checked out.
In brief
Deduction is from the general to the specific; induction is from the specific to the general. “Induction starts with known instances and arrives at generalizations; deduction starts from a general principle and arrives at some individual fact”2. Deductive reasoning can be more sound if the premises are ‘true’. Premises in inductive reasoning may be true but may not be universally true; therefore, more research and reasoning would be required.3
1 PIE deuk and Latin ducere are also the origin of words such as: abduct, aqueduct, conducive, conduct, conductor, duct, duke, education, introduce, production, reduction, seduction, and others.
2 https://www.etymonline.com/search?q=induction
3 https://examples.yourdictionary.com/deductive-reasoning-examples.html
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