Combining Texts

You have chosen 'A Mathematical Introduction to Logic (2nd)' by Herbert B. Enderton, 'works' by Jean Calvin and 'Criterion of Validity in Reasoning' by Charles Sanders Peirce

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All the ideas for Modality, or select a subheading:
      A. Necessity
      B. Possibility
      C. Sources of Modality
      D. Knowledge of Modality
      E. Possible worlds