Action Theory

Volume 97 of the series Synthese Library pp 241-270

‘Can’ in Theory and Practice: A Possible Worlds Analysis

  • Keith LehrerAffiliated withUniversity of Arizona

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The word ‘can’ stands at the intersection of our theoretical and practical interests. In science and rational inquiry, we seek to explain human behavior and assume there to be natural laws to be discovered in this domain as in others. Given such laws and suitable antecedent conditions every human action may be explained in such a way that it appears that the agent could have performed no other action than the one he did. Our legal and moral concerns, on the other hand, lead us to assume that people sometimes could have fulfilled their obligations when, in fact, they did not do so. To resolve the conflict, philosophers have argued that statements about what a person could have done should be analyzed in terms of conditionals. Others have demurred. The present moment is a propitious one for reconsideration because of recent research on conditionals using possible world semantics. Using such methods, I shall argue that ‘can’ and ‘could have’ statements should not be analyzed in terms of conditionals. I shall, moreover, provide an analysis of ‘can’ and ‘could have’ statements within the framework of possible world semantics. Finally, I shall argue that under the analysis provided, conflict between theory and practice, between freedom and determinism, may be resolved. The resolution shows that truth of the statement that a person could have done otherwise is independent of the truth of determinism.