Why Is a Valid Inference a Good Inference?

Sinan Dogramaci
University of Texas at Austin
True beliefs and truth-preserving inferences are, in some sense, good beliefs and good inferences. When an inference is valid though, it is not merely truth-preserving, but truth-preserving in all cases. This motivates my question: I consider a Modus Ponens inference, and I ask what its validity in particular contributes to the explanation of why the inference is, in any sense, a good inference. I consider the question under three different definitions of ‘case’, and hence of ‘validity’: the orthodox definition given in terms of interpretations or models, a metaphysical definition given in terms of possible worlds, and a substitutional definition defended by Quine. I argue that the orthodox notion is poorly suited to explain what's good about a Modus Ponens inference. I argue that there is something good that is explained by a certain kind of truth across possible worlds, but the explanation is not provided by metaphysical validity in particular; nothing of value is explained by truth across all possible worlds. Finally, I argue that the substitutional notion of validity allows us to correctly explain what is good about a valid inference.
Keywords validity  case  interpretational  substitutional  value  inference
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DOI 10.1111/phpr.12206
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References found in this work BETA

Logical Pluralism.Jc Beall & Greg Restall - 2005 - Oxford University Press.
Philosophy of Logic.W. V. O. Quine - 1970 - Harvard University Press.
Methods of Logic.W. V. Quine - 1950 - Harvard University Press.
The Ways of Paradox.W. V. Quine - 1966 - New York: Random.

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