‘There is no <i>reason</i> for the necessity of the ultimate principles of deduction.’ Margaret Macdonald on logical necessity

Abstract This paper aims at contributing to the recent enterprise of rediscovering Margaret Macdonald's views, by focusing on her reflections on the necessity of logic, a theme that runs through many of her papers and reviews. We will see both Macdonald's negative views about what the necessity of logic is not (Section I), and her positive view about what it is and how it supports her claim that it is in fact irrational to ask for a reason for the necessity of the ultimate principles of deduction, such as the Principle of Contradiction (Section II). To show how her view on the necessity of logic is different from others, such as David Lewis's, we will then consider what she would reply to current rejectors of the Principle of Contradiction (Section III).