The differences between reasoning from principle and reasoning from specific instances

Question

Can anybody tell me the differences between reasoning from principle and reasoning from specific instances ?? Thanks for reading my question.

Answer 1

Reasoning from principle is deductive reasoning.  Given a general principle such as conservation of momentum, you can figure out the momentum imparted to a rifle by a bullet of a particular mass fired at a particular speed.  Deductive reasoning is valid if the premises are valid and correct rules of logic have been applied.

Reasoning from specific instances is inductive reasoning.  If in several instances you apply 38,700 volts to a spark gap and get a spark each time, you can reasonably conclude that the breakdown voltage of the spark gap is somewhat less than 38,700 volts.  Inductive reasoning is NOT automatically valid; a counterexample may someday be found which would negate the conclusion.

Answer 2

Reasoning from principle can also be called deductive reasoning.  This is reasoning based on a general premise that is assumed to be true.  You move along logically applying that general statement to a specific situation to form a conclusion.

Reasoning from specific instances is called inductive reasoning.  This involves taking specific cases of observed fact and looking for generalizations that can represent all cases.

Answer 3

Reasoning from principle is based on your morals, and the other is based off real-life occurences. Example

Reasoning from principle:

you shouldn't shoplift because it is morally wrong.

From specific instances:

you shouldn't shoplift because it causes the vendor to lose money, and then causes them to raise prices to make up for the loss.  

Answer 4

In psych, these two concepts are called "top down" (from principle) and "bottom up" (from instances). Its how theory and research works together. Say you find out that posters are effective marketing for soda (bottom up, based on studying specific posters and people's reactions) and then create a theory (principle) that posters affect shoppers' buying behavior. Then, you can test this via further specific research (instances) to see if this is true for various instances (eg. not just soda, but also laundry detergent, pasta, and wine). You may find that posters affect soda and wine, but not the others, and with further testing, create a new theory that posters affect impulse or "frivolous" purchases, but not "staple," or "necessary" items).

In this case, bottom up reasoning would be basing your opinion on shoppers' individual actions (eg seeing that shoppers who walked by posters for pepsi bought more than those who walked by posters for public service announcements); top down would be deciding that because "posters and marketing affect buyers' choices and behavior", buyers must purchase more pepsi if they see posters for this product. I hope this helps, from a bit of a different point of view (psych vs philosophy)