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# Applying the First Four Rules of Inference

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I don't understand how to apply the first four rules of inference to this statement:

"Every piece of reasoning must start somewhere. And if every piece of reasoning starts somewhere, then every piece of reasoning begins with an unsupported premise. Now, if every piece of reasoning begins with an unsupported premise, then all human thinking is based on mere assumption. And if all human thinking is based on mere assumption, then no one can know anything. Therefore, no one can know anything."

I started setting it up using the 's' in start, 'b' in begins, 'a' in assumption and 'k' in know.

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Rules of inference are explained.

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Firstly, it's not a statement but an argument, and only modus ponens and 'hypothetical syllogism' are applicable.

Every piece of reasoning must start somewhere.

And if every piece of reasoning starts somewhere, then every piece of reasoning begins with an unsupported ...