Understanding different types of arguments is an important skill for philosophy because it enables us to assess how strongly a conclusion is supported by its premises. It also enables us to critique arguments more accurately by identifying whether they aim at logical necessity, probability, or the best explanation. This post looks at 3 general types of argument and illustrates each with an example:
Deductive Arguments: The Conclusion is Certainly True
Deductive arguments operate on the principle of logical necessity, aiming to provide conclusions that follow necessarily from the premises.
So, rather than appealing to probability or likelihood, deductive reasoning concerns whether the structure of the argument guarantees the truth of the conclusion (assuming the premises are true).
In other words, deductive arguments are logically watertight: If the premises are true, it’s logically impossible for the conclusion to be false.
Example of a deductive argument:
- Premise 1: All dogs are mammals.
- Premise 2: Rex is a dog.
- Conclusion: Therefore, Rex is a mammal.
In this deductive argument, the conclusion follows necessarily from the premises. If we accept the truth of the general principle that all dogs are mammals (1) and the premise that Rex is a dog (2), we are logically compelled to accept the conclusion that Rex is a mammal (3).
Other examples of deductive argument formats include modus ponens and modus tollens.
Note: A deductively valid argument means the conclusion necessarily follows from the premises and so, if the premises of the argument are true, the conclusion must also be true. However, the premises may be false, in which case the conclusion may be false too. For example:
- Premise 1: If today is Monday, the moon is made of green cheese.
- Premise 2: Today is Monday.
- Conclusion: Therefore, the moon is made of green cheese.
This argument is still deductively valid – the conclusion does follow necessarily from the premises – but the conclusion is false because one or more of the premises are false. For more detail on valid reasoning (including the difference between a valid and sound argument) see this post.
Inductive Arguments: The Conclusion is Probably True
Inductive arguments are those in which the premises make the conclusion probable rather than logically necessary.
They often involve drawing general conclusions from limited observations, but more broadly they aim to establish what is likely to be true given the evidence, rather than what must be true. So, while inductive arguments do not guarantee absolute certainty, they offer insights and probabilistic reasoning.
In other words, inductive arguments are not logically watertight – but they nevertheless provide support for the conclusion.
Example of an inductive argument:
- Premise 1: Most dogs have 4 legs.
- Premise 2: Rex is a dog.
- Conclusion: Therefore, Rex probably has 4 legs.
This example illustrates an inductive argument in which the conclusion is drawn from a general statistical premise and applied to a particular case. Because most dogs have four legs, it is reasonable to infer that Rex probably has four legs. However, the conclusion is not logically guaranteed – it’ possible that Rex is missing a leg or was born with a defect. The premises therefore make the conclusion likely, but not certain.
Another type of inductive argument is an argument from analogy, where because two things are similar in one way they are likely to be similar in another way. For example, if your friend likes the same music as you, this may suggest they will like the same art as you.
Abductive Arguments: The Conclusion is the Best Explanation
Abductive arguments focus on finding the best or most plausible explanation for a given observation or phenomenon.
They involve reasoning from evidence to a hypothesis or explanation that provides the most likely account of the observed facts. An explanation may be considered more likely or plausible because it fits more neatly with the observed data, for example, or because it is the simplest explanation with the fewest assumptions (a principle known as Ockham’s Razor).
Like inductive arguments, abductive arguments are not logically watertight. Although a hypothesis may seem to be the best explanation, other explanations are still logically possible.
Example of an abductive argument:
- Premise 1: Rex didn’t eat his food this morning. He’s unusually quiet and lying in the corner. Normally he’s energetic and excited at mealtime.
- Premise 2: If a dog is sick, that would explain this unusual behaviour.
- Premise 3: No alternative explanation fits the facts as well.
- Conclusion: Therefore, Rex is probably sick.
In this abductive argument, Rex’s unusual behaviour – not eating, being quiet, and lying in the corner – constitutes the observed evidence. The hypothesis that Rex is sick provides the best explanation of these facts. However, alternative explanations are possible, such as stress, fatigue, or a minor injury. The conclusion is therefore not certain, but inferred as the most plausible explanation available.
Applied to A Level Philosophy
There are various examples of deductive arguments, inductive arguments, and abductive arguments in A level philosophy.
Examples of deductive arguments in A level philosophy:
- The logical problem of evil
- Ontological arguments (e.g. Anselm’s or Malcolm’s)
- Descartes’ trademark argument
Examples of inductive arguments in A level philosophy:
- The evidential problem of evil
- Hume’s teleological argument
- Mill’s response to the problem of other minds
Examples of abductive arguments in A level philosophy:
Identifying whether an argument is deductive, inductive, or abductive is a great way to demonstrate detailed and precise knowledge of philosophy and pick up those AO1 marks.
Further, knowing the difference between these types of arguments can also be useful to help evaluate (AO2) the strengths and weaknesses of the various arguments you consider in the 25 mark essay questions.
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