Alan Ross Anderson

Alan Ross Anderson was an American logician and professor of philosophy at Yale University and the University of Pittsburgh.
A frequent collaborator with Nuel Belnap, Anderson was instrumental in the development of relevance logic and deontic logic.
Anderson died of cancer in 1973.

Relevance logic

Anderson believed that the conclusion of a valid inference ought to have something to do with the premises. Formally, he captured this "relevance condition" with the principle that
As simple as this idea appears, implementing it in a formal system requires a radical departure from the semantics of classical logic. Anderson and Belnap explored the formal consequences of the relevance condition in great detail in their influential Entailment books, which are the most frequently cited works in the field of relevance logic.
Anderson and Belnap were quick to observe that the concept of relevance had been central to logic since Aristotle, but had been unduly neglected since Gottlob Frege and George Boole laid the foundations for what would come to be known, somewhat ironically, as "classical" logic.

Deontic logic

Anderson advocated the view that sentences of the form "It ought to be that A" should be interpreted logically as:

Not-A entails v,

where v means something like a norm has been violated. He developed systems of deontic relevance logic containing a special constant v for this purpose. Such systems have sometimes been characterized as "reductions" of deontic logic to alethic modal logic. This is misleading at best, however, since alethic modal logics generally do not contain anything like Anderson's special v constant.

Philosophy of logic

Anderson was known for being a Platonist about logic; he believed in "The One True Logic," and he believed that it was a relevance logic.