Types Of Arguments

Developing Arguments

To prove any claim: Deductive reasoning (general to specific)

* If premises are assumed to be true and conclusion is certainly true as a result, the conclusion is valid.
* If premises are actually true and the conclusion is valid, the conclusion is sound.

To prove qualified claims: Inductive reasoning (specific observation, general conclusion)

* If premises are assumed to be true and the conclusion is probably true as a result, the conclusion is strong.
* If premises are actually true and the conclusion is strong, the conclusion is clear, logical and convincing.

To prove heavily qualified claims: Abductive reasoning

* Inference to the best explanation
* Form of induction
* Always formally fallacious - affirms consequent
* Propose/confirm existence of a phenomenon, propose possible causes, determine most probable cause

To Disprove Claims

Reduction ad absurdum:

* Show absurd consequence of unsound claims.
* Ex: heavy things fall faster than light things, A>B, B acts as a drag on A, A+B is slower. A+B>A, A+B is faster.
* If both a conclusion and its negation can result from the same premises, the argument is unsound.

Argument from analogy:

* Point of analogy is not to equivocate, but to illustrate/clarify
* Ex: Singers drowning child (if you were walking past a fountain and you saw a child drowning in it, do you have moral obligation to save the child)

Thought experiment:

* Extended analogy - must involve element of experimentation
* Create hypothetical scenerio, explore all possible options
* Ex: Lucretius spear (throwing a spear to the edge of the universe)

Inductive v Deductive arguments


Strong + True = Cogent
* A form of reasoning which reaches conclusions by using a few observations to make a generalization.
* Although the conclusion can be a good one, it is not necessarily so, because not all possible observations can be made.
e.g. for the past 50 years, it was always rained in the first week of April in the Lake District
Therefore it will rain in the week of April next year in the Lake District


True + Valid + Sound
* a form of reasoning in which if the premises are true, and the logic is good, then the conclusion must be true.
Premises: Birmingham is a city in the West Midlands.
The West Midlands is a region in England.
Conclusion: Therefore Birmingham is a city in England.

Sound Argument

A sound argument has both validity and truth

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