## Inductive or Deductive argument?

2

"High government spending causes interest rates to go up. The government is spending a lot. Therefore, interest rates will go up."

The argument above is inductive or deductive? In a textbook that I study, the author states that it is inductive.

But in my opinion, if we paraphrase the first premise in equivalent form as "If the government is spending a lot, then interest rates will go up", then this argument clearly has valid deductive form - modus ponendo ponens: If A, then B. A. So, B.

3The argument is clearly deductive : "if P, then Q; P; therefore Q". The issue is : not evry valid argument is sound : i.e. if we use a valid argument with false premises, the conclusion will not be necessarily true. In the above case, the major premise "High government spending causes interest rates to go up" is an empirical statement based on "facts" : it may happen that government X spend a lot and (for some other concomitant economic factor) interest rates will not grow. – Mauro ALLEGRANZA – 2016-10-27T08:40:55.223

to add to @Mauro ALLEGRANZA 's correct comment: the major premise would likely be the conclusion of inductive reasoning. Maybe that's what the author has in mind? – None – 2016-10-27T18:20:57.280

1

High government spending causes interest rates to go up. The government is spending a lot. Therefore, interest rates will go up.

We could formulate this as:

If "A causes B" is true and A is the case, then B is true.


But, I am not so deductively certain this form can be cogently induced from the statements above.

Are "High government spending" & "The government is spending a lot" necessarily or sufficiently equivalent? Certainly a standard could be established to quantify the former, however, the latter is vague, i.e. "spending a lot" according to whom? King Midas? The last person in line at the local soup kitchen? You??

Also, are we certain that A necessarily or sufficiently causes B?

In your textbook, does the author justify their statement? Do they describe or formalize the differences and similarities or at least compare induction and deduction?

Hope that helps.

4

Here is the argument: "High government spending causes interest rates to go up. The government is spending a lot. Therefore, interest rates will go up."

This reasoning is an example of induction. The first premise is shorthand for: "In every observed example in the past, high government spending caused interest rates to go up." The reasoning calls upon this collection of past experiences to project future behavior.

1

In his classic book How to Solve it, G. Polya writes: "induction is the process of discovering general laws by the observation and combination of particular instances."

I would say that your question contains its own answer: deductive reasoning (hypothetico-deductive as a matter of fact) is the type of reasoning you are trying to do, since you are using logic rules to infer from a hypothesis. The fact that you are not 100% sure of your hypothesis does not alter that fact.

Inductive reasoning works in a very different way. You are taking a large number of individual facts and trying to guess some higher rule from them. In order to go "inductive", you would have to have all the relevant instances where government spending has gone up, not the conclusion that someone else made, which has by now become your hypothesis.

The only "logic" part there is in inductive reasoning, is that you should try to explain what the matter is with the individual facts that do not agree with your rule (measurement errors, something else?). So you dont' "prove" anything with inductive reasoning, there is nothing "true" or "false", you are just trying to find some rule that matches the (hopefully reliable) facts you have, in the best possible way.

Inductive reasoning is one of the most misunderstood forms of human thinking and rarely taught at school. And yet it is absolutely crucial to the evolution of any science. It is also crucial if you want to learn anything from daily life experience.

Indeed, most of what is taught at school as "inductive", is not. For example, we could use linear regression to find a line between points. In order to do that you have to assume first that what you are looking for is a line, and then the rest is a deduction. Linear regression is an algorithm that can be easily implemented with a computer. Stricly speaking it is not induction. It is a heuristic tool that you could use in a general process of induction, though.

To our knowledge, we don't know, in the general case, how to formalize inductive reasoning and we don't know how to program it. Whatever we program turns out to be deductive reasoning -- or a brute force attack -- or a mix of the two. How humans do that, is anyone's guess (litterally: induction requires imagination, to "think outside of the box", to walk outside the beaten path, plus healty dose of artillery skills, to reckon how far you are shooting from the target).

From there it opens an avenue for debate on whether artificial intelligence is different from human intelligence. And I would argue that machines (in the current state of our technology) can sometimes give the impression to work by induction, but in reality they aren't.