Presentation 4b: Possibility and Necessity (Phil 1230: Reasoning and Critical Thinking)

Summary

This presentation explores the concepts of possibility and necessity, focusing on logical and nomological possibilities. It defines logical possibility as what does not contradict the laws of logic, while nomological possibility relates to the laws of nature. The discussion includes examples of both types of possibility, as well as related notions such as legal, moral, and technological possibilities. The video also addresses how these concepts inform the definitions of necessary and sufficient conditions, ultimately tying back to the notion of argument validity. The emphasis is on understanding how premises can guarantee conclusions without relying on outside assumptions.

Takeaways

• 😀 Validity in arguments means there is no logically possible situation where the premises are true and the conclusion is false.
• 😀 Logical possibility refers to states of affairs that do not contradict the laws of logic.
• 😀 Nomological possibility relates to states of affairs that do not contradict the laws of nature.
• 😀 Different forms of possibility include legal, moral, technological, conceptual, and metaphysical possibilities.
• 😀 A state of affairs is logically necessary if it must obtain according to the laws of logic.
• 😀 A state of affairs is nomologically necessary if it is required by the laws of nature.
• 😀 Necessary conditions imply that without X, Y cannot occur, while sufficient conditions mean that X guarantees Y.
• 😀 Logical impossibility occurs when a state of affairs contradicts the laws of logic.
• 😀 The concept of validity emphasizes that the conclusion of an argument must follow solely from the premises, without external assumptions.
• 😀 Understanding different kinds of possibility and necessity is essential for critical thinking and analyzing arguments.

Q & A

What is the definition of validity in an argument?

An argument is valid if and only if there is no logically possible situation where all the premises are true and the conclusion is false.

What does logical possibility mean?

Logical possibility refers to a state of affairs that does not contradict the laws of logic, meaning anything that isn't contradictory is logically possible.

Can you give an example of logical impossibility?

An example of logical impossibility is the statement 'a triangle has four sides' because it contradicts the definition of a triangle.

What is nomological possibility?

Nomological possibility is based on the laws of nature, meaning a state of affairs is nomologically possible if it does not contradict the established laws of nature.

What is an example of nomological impossibility?

An example of nomological impossibility is traveling faster than the speed of light, as this is precluded by the laws of physics.

How does moral possibility differ from legal possibility?

Moral possibility pertains to what is compatible with moral rules, while legal possibility relates to what is permitted by legal laws.

What is the relationship between necessity and possibility?

A state of affairs is necessary if its non-existence is impossible. Thus, necessity is directly tied to the impossibility of an alternative scenario.

What does it mean for a state of affairs to be logically necessary?

A state of affairs is logically necessary if it must obtain, meaning it is impossible for that state not to occur according to the laws of logic.

Can you explain the significance of the distinction between logical and nomological necessity?

Logical necessity relies solely on the laws of logic, while nomological necessity is contingent upon the laws of nature, reflecting different constraints on what must occur.

Why is logical possibility important for assessing the validity of arguments?

Logical possibility is crucial because an argument is valid only if the premises alone guarantee the conclusion without relying on any external assumptions.