232
This line of argument is basically a strawman fallacy, which is when you construct a weaker version of your opponent's argument in order to then disprove it. In this case the weaker argument is that "guns kill people" all by themselves. No one actually believes that or argues that. Even the most committed gun control advocate acknowledges that firing a ...
43
To complement Chris' answer I'll try to deconstruct some of the reasoning in the arguments a bit.
Suppose we claim that "guns don't kill people; people kill people." The only reasonable way to parse this into a slightly more formal statement is:
Guns are not responsible for killing people; people are responsible for killing people.
I can think of ...
34
First: we don't really say that arguments are true or false. Statements are true or false, but arguments have different kinds of properties.
One of those properties is, as you are obviously aware of, validity. However, another important property is well-foundedness, which means that the premises are true (or, for more practical everyday purposes, plausible ...
21
Yes :
Premise : All dogs are mortal (true)
Premise : All birds are dogs (false)
Conclusion : All birds are mortal (true)
The argument is valid because there is a correct relation between premises and conclusion. This is not because the conclusion is actually true but, crucially, because granted the premises the conclusion must follow even though one of ...
18
"Guns don't kill people; people kill people" is not an argument, it's a slogan. It may be the case that this slogan is just a way to get people to discuss the role of individual responsibility in what policies the government ought to adopt with respect to guns or something like that. Or perhaps it is just a signal that a person has some particular position ...
16
(Promoting this from @MauroALLEGRANZA's comment, since it deserves a full answer.)
Yes, an argument can be valid but still not be sound.
This is really just a matter of understanding the terminology:
A deductive argument is said to be valid if and only if it takes a form that makes it impossible for the premises to be true and the conclusion ...
14
Yes, there are many "philosophical theories" that have been refuted by the majority of experts.
An obvious example is Thales identification of "water" as the irreducible substance. Many pre-Socratic "theories" of this sort spring to mind. But the "refutation" only comes about by the subdivision of philosophy itself into other fields of "expertise," notably ...
14
Hence, I think this one is a sound sentence.
Soundness is not a property that applies to sentences, but rather to arguments as whole. A sound argument is one that is valid and has all true premises. Since this argument is invalid, it is not sound, even though all the sentences in the argument happen to be true. My sense is that the fact that all these ...
13
A problem in your question has to do with the concept of refutation and confirmation. If you think of refutation as empirical refutation, then trivially, only empirical sciences refute hypothesis. Concluding that philosophical inquiry is therefore not valuable is question begging: it amounts to adopt a specific philosophical position that would say that only ...
11
This is a black-or-white fallacy. While logically it checks out as true and is difficult to disagree with in real-time discussion; the intention is to frame the argument using an oversimplification of the context, and to the exclusion of other options. Such as excluding middle cases or alternatives.
Also called false dilemma, fallacy of false alternative or ...
11
I think you can view the "X doesn't do A; Y does A" formulation as either
(a) a response to an equivocation meant to elucidate it
OR
(b) an equivocation itself
Working with the classic "guns don't kill people; people kill people", we can parse this into slightly more helpful language:
Guns don't cause people to die; people cause people to die.
In ...
11
The argument is valid. It's easier to see if translated to symbols:
1. R v W premise
2. R → F premise
3. ~F premise
4. ~R entailed by 2-3
5. W → ~D premise
6. D premise
7. ~W entailed by 5-6
8. ~R & ~W entailed by 4&7
The argument contains two sub-arguments: 2-4 and 5-7, (1 is superfluous, assuming in this ...
10
Don't be misled by the second way of presenting Modus Tollens (MT). The general form is:
MT: {P → Q, ¬Q} ⊢ ¬P.
Your second form, call it MT′, is very different:
MT′: {¬P → ¬Q, Q} ⊢ ;P.
From a natural deduction standpoint with a rule of conditional introduction and detachment (also called ...
9
A statement of the form "If X then Y" where Y is true, is always true in classical logic. If the consequent of a conditional is true, then it matters neither what the antecedent is, nor whether there's any actual connection between them.
In this case, your "Y" expresses a mathematical truth, so we can take it as being a proposition that is always and ...
8
This argument could hardly be rendered into a valid form without all kinds of additional assumptions and clarifications. For example,
Assumes we know what God wants and what he/she might or might not do to satisfy those wants. It is difficult enough to speculate about what other people might want or might do about their wants, without trying to speculate ...
8
It is common for beginning students of logic to read philosophical importance into the principle of explosion, but this is a mistake. The principle of explosion is merely a mathematical outcome of the way the connectives are traditionally defined in first-order logic. It doesn't reveal anything deep, however. It merely arises from the following proof:
...
7
To quote Eddy Izzard: Guns don't kill people, people with guns kill people. The whole thing is a sophistry: A clever but wrong argument with the intent of deceiving people.
First, it is a fact that guns do kill people. Just like leaking gas pipes, badly working brakes and so on kill people, so do guns kill people. Not very often, but often enough to make ...
7
In general, you do not know whether the premise is true or not. Still, we would like to say that something is wrong with an argument, if its premises are wrong. Note that
All men are immortal.
Socrates is a man.
Therefore, Socrates is immortal.
is a valid argument. But presumably, it is not sound.
When calling an argument "sound", you defer the questions ...
7
Philosophical arguments are made mathematical all the time. Its why you will see First Order Logic symbols thrown around on this Stack Exchange.
I think the big difference between mathematics and philosophy is that mathematics tends to start from something like a formal system, and see how much can be proven within it. Philosophy approaches the question ...
7
There is no universal agreed upon answer, but personally I would be a little Aristotelian about it: art has a purpose, and the degree that it is fit to that purpose is the degree that it is great art.
Some would say that the purpose of art is to make our surrounding more pleasant. It is to make us feel good, so we may judge whether lots of people "like" ...
7
Regarding the statement from your question:
"it isn't valid"
By definition, an argument is valid if the premises and our accepted working of logical rules create a situation such that if all of the premises are true, then the conclusion cannot be false. From the detail in your question I assume you are aware of this much.
Having redundant premises is ...
7
This argument is valid on most definitions of validity.
The common definition of validity in use today is: if the premises are true, then the conclusion must be true.
worded another way, there must be no possible way for it to have all true premises and a false conclusion.
The value of validity (on this definition) is that it checks whether an argument is ...
6
Take the logical fallacy that seems to come up the most: Appeal to Authority. People will make decisions all the time because someone with lots of experience or an important sounding title told them to do so.
I think rather than saying "No Fair! That's the appeal to authority fallacy," you guide the person to the meat of why it's not a compelling argument ...
6
I'll try to provide a partial answer as I do think this is an interesting question about philosophy.
Reasons Philosophy is Hard to Understand
First, I would say that you might be losing something in describing the works of philosophers as "opinions". On a certain trivial level, they are opinions, but on this trivial level so is C The Programming Language, ...
6
The question is vague, so it can be several different things. Generally, dismissing an argument based on who is supporting it is called ad hominem, "attack on an argument made by attacking the character, motive, or other attribute of the person making the argument, rather than attacking the argument directly". It might also be what is more specifically ...
5
An argument is deductively valid if and only if it's impossible for all its premises to be true and its conclusion to be false at the same time. If it's impossible for its premises to be true at the same time, then that is itself sufficient to meet that definition, and make the argument valid, independent of the truth-value of the conclusion.
Whether this ...
5
Science as a discipline does not take as axiomatic the view that nature is fundamentally material, although many scientists do. Science does postulate the existence of objects having mass and physical forces that produce effects on these objects, but postulating the existence of one type of object does not preclude the possibility of other types of objects ...
5
All birds are green,
My dog is a bird
Therefore my dog is green
This is a valid argument because the conclusion follows from the premises. Yet the premises are false.
5
Let's look at the translations (into first-order logic):
(1) ∃x : Man(x) ∧ Married(x).
(2) ∃x : Man(x) ∧ ¬Married(x).
The first is true in universes where there is at least one married man; the second is true in universes where there is at least one bachelor. To show that the argument from (1) to (2) is not valid, consider ...
5
Reagarding Tarski's original motivation, we can see the new English translation of Tarski's 1936 paper :
Alfred Tarski, On the Concept of Following Logically (1936) :
Even relatively recently it seemed to many logicians that they had managed, with the help of a relatively simple conceptual apparatus, to capture almost precisely the everyday content of ...
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