What is a valid(符合逻辑的) argument?
An argument is a t of statements aimed at explanation and/or persuasion. It consists of a conclusion/claim and premis (i.e., reasons) that support the conclusion. In formal logic, a valid argument is one in which the argument's conclusion must be true if the supporting premis are in fact true.
Truth and Validity
Whether an argument is valid does not speak to the truth, or falsity, of an argument's conclusion or its premis. Validity refers simply to whether the conclusion flows logically from the premis. Thus, an argument may contain fal premis and a fal conclusion and still be valid.
Determining Validity
To determine whether an argument is valid, you must answer the following question: Assuming the premis are true, is another conclusion possible? If so, the argument is inval
id.
Soundness and Validity
A sound argument is a valid argument with true premis. Therefore, a sound argument must be a valid argument.
Examples
Examples of valid arguments are as follows:
Premi: All dogs are mammals.
Premi: My pet Sam is a dog.
Conclusion: Therefore, Sam must be a mammal.
Premi: All banks are financial institutions.
Premi: Wells Fargo is a financial institution.
Conclusion: Wells Fargo is a bank.
Examples of invalid arguments follow:
Premi: Only men have blue eyes.
Premi: Christina has blue eyes.
Conclusion: Therefore, Christina must be a man.
Premi: All Toyotas have 4-wheel drive.
Premi: My car is a 4-wheel drive car.
Conclusion: Therefore, my car is a Toyota.
Considerations
Validity is a term ud to describe deductive(推论的)arguments as oppod to inductive( 归纳的)arguments. A deductive argument aims for a conclusion that must be tr
ue given true premis, whereas an inductive argument claims a highly probable conclusion, given true premis. Therefore, deductive arguments are either valid or invalid; there is no such thing as almost valid. Inductive arguments, however, fall on a spectrum(范围) from strong to weak.
Source:
"A Conci Introduction to Logic"; Patrick J. Hurley; 2006
符合逻辑不一定合理，合理就一定符合逻辑。
What is the difference between valid and sound argument?
In: Philosophy and Philosophers, The Difference Between [Edit categories]
Answer:
A valid argument is an argument who conclusion follows logi地震避险
cally from the truth of the premis. It is impossible for the premis to be true and the conclusion fal. An exampl
e of a valid argument is:
1. If Thales was right, then everything is made of water.
2. It's not the ca that everything was made of water.
3. So, Thales wasn't right.
This argument has the form: If P then Q, ~Q, therefore ~P. The conclusion is derived using Modus Tollens. All of the premis are true, and so is the conclusion.
However, the validity of an argument does not entail the truth of its conclusion. Consider another example of a vali安全回路
d argument:
1. If Socrates was a Philosopher, then Socrates was a happy alligator.
2. Socrates was a Philosopher.
3. So, Socrates was a happy alligator.
This argument is valid: it is of the form If P then Q, P, therefore Q. The conclusion is derived using Modus Ponens (a rule for logical inference which prerves truth).
However, the conclusion is fal. Becau it is valid, one of the premis must also be fal: and, we can e, premi 1 is the culprit. If we replace it with a better premi, such as "If Socrates was a Philosopher, then Socrates existed", we derive a different and true conclusion (that Socrates existed).
A sound(合理的) argument is an argument with two features: (i) it is valid, and (ii) its premis are all true.
It is not clear whether we ought to include other features, like non-circularity, in the necessary conditions for soundness; convention has yet to determine it.
In my opinion, a valid argument is any argument that opens a dialogue (without anger of cour) where the opposing side can e and understand your side and may actually cau doubt as to whether they were right at all.
Opposing argument:
Arguments begin with a premi or premis and end with a conclusion. Take the argument 洗面奶的正确用法
above, here we have a premi that states a valid argument is one that opens a dialog, qualifying that opening as non emotional, and concludes that by opening with a non emotional argument of non specified nature the opposing side will understand the correctness of this argument and thereby have doubt about its own argument. Of cour, since the premi is far too vague to even lead to a conclusion, there is no doubt by the opposition that another definition is required to effectively explain what a valid argument is.
