Deductive vs. Inductive Arguments

[darklight]

Hi guys,
I am not studying Philosophy this year but I just wanted to ask a question regarding deductive and inductive arguments (not sure if this board is the right place to put it, feel free to move it). I'm quite new to this, so bear with me

With deductive arguments, they can be 'invalid' or 'valid' which leads to 'unsound' and 'sound'. Just to clarify, valid arguments are those in which the conclusion has to be true if the premises are true, and sound is when the premises are true as well?

In terms of 'inductive' arguments, I've seen a podcast that separates them into 'strong' or 'weak' and then 'cogent'/'uncogent' underneath strong. My question is, can the term 'strong' ever be applied to deductive arguments?  Or is the definition of strong such that it can only be related to inductive arguments?

Thanks! 

[achre]

Hey, this is absolutely the right board for this question

A deductive argument (also called a syllogism) is an argument that employs deductive reasoning, which is reasoning that takes two or more premises to form a conclusion. The two words we usually use to describe a deductive argument are "sound" and "valid", which aren't properties that necessarily follow from one another. (It wouldn't be right to say that 'valid' or 'invalid' follows from 'sound' or 'unsound') If an argument is sound, it means its premises are true. If an argument is valid, it means that the conclusion follows from the premises. So yup, you got that right.

A deductive argument, therefore, can be either sound and valid (and hence true), unsound and valid (hence not necessarily true), sound and invalid (not necessarily true), and, of course, unsound and invalid. You wouldn't (shouldn't) describe a deductive argument as strong or weak, because the case it presents should (in theory) be able to be either entirely accepted or rejected without further argument. But at the same time, rejecting a deductive argument doesn't imply that the conclusion is false.

The classic example of deductive resoning is the "Socrates is mortal" syllogism:

P1. Socrates is a man.
P2. All men are mortal.
C. Socrates is mortal.

Which might be generalised to:

P1. A is X
P2. All X are Y
C. A is Y

Inductive reasoning, from what I understand, is reasoning that makes a strong case for a particular conclusion, but that doesn't assert it with certainty. Usually it consists of an inference made from observation - science is probably the best known example of inductive reasoning. As for your question about strong & weak or cogent & uncogent inductive arguments, I genuinely don't know enough about the matter to tell you. It occurs to me now that you're probably using a special case of the word 'strong' which might make my comment about the non-applicability of "strength" to deductive arguments false. Oh well, I've typed too much out to delete it now.

Hope you found it helpful anyway haha 

[slothpomba]

In a general sense, deductive is general -> specific and inductive is the opposite, specific -> general. This isn't necessarily a philosophy thing, this might be employed in many fields.

Deductive can be thought of as "stronger" in one sense but doesn't mean inductive is worthless either.
An example of deductive:

P1. Only men have beards. (general)
P2. Plato has a beard
C. Plato is a man (specific)

C stands for conclusion, P stands for premise. If you look at the argument, you notice it moves from the specific to general. You can almost imagine it as a funnel, wider at the top, coming to a single point at the bottom. It also relies on several laws of logic to operate. One is the law of non-contradiction, you can't have something be simultaneously true and false, all men either have beards or dont have beards, you can't really have both be true (these kind of minute points are debated in academia though).

It feels strong because you assert that only men have beards, you are making a strong general claim here. Assuming this premise/assertion is true (if a premise isn't, any conclusion from it can be considered wrong or flawed too), it just seems like it *has to be* that plato is a man since he has a beard. You can see this kind of logic in philosophy and mathematics (depending on branch). It's based on things that are axiomatic or just plainly obvious (in this case, all men having beards really isn't unless you know all men, so, my example is partially invalid).


Inductive is probably more familiar and natural to you. It's usually what is used in science and as a Sherlock Holmes fan, often in Sherlock Holmes cannon (despite it being claimed he is a master of DEDUCTION). If it helps, you can think of it deduction done backwards, tipping the funnel on its head.

P1. Plato is a man (specific)
P2. Plato has a beard
C. Only men have beards. (general)

The problem here might stick out to you like a saw thumb. Unless you see all humans, at all points in their lives and at all points in history future and past, you cant be sure that only men have beards. You certainly cant deduce it from Plato. What if he is some kind of freak with a weird disorder that makes him grow a beard and no other man is like that? It might be useful to imagine yourself as an alien, knowing nothing about a subject and inducing it from what you are given.

If an Alien landed in China, he might be liable to think all humans are Chinese. You get issues like that. Herein lies the problem of induction (which is a challenge to science), you cant be certain of things you gain by induction, you can be very sure but not certain. You could induce that the sun will rise tomorrow morning, it's done it for millions of years (general), so, why wouldn't it rise tomorrow (specific)? However, you cant be *sure*. For all we know, the sun will explode when you go to bed. This is why in science we often use statistical tools like confidence intervals and P values to show how likely it is something is correct (rather than necessarily it is or isn't correct).

Simply put as a general rule, deductive tells you what is certain (or not); inductive tells you what is likely (or not).

[darklight]

Thank you both! Cleared a lot of things up