Colin Howson died aged 74 on 5 January 2020, a great loss to scholarship and to his many friends. He had suffered for a short time the terrible effects of an irremediable brain tumor. Colin was born in London but as a boy moved with his family to Devon and attended school there. In 1963 he enrolled at the LSE, first in Economics, then transferring to the Department of Philosophy, Logic, and Scientific Method. His exceptional gifts were early recognized and he was offered a lectureship in the department soon after completing his undergraduate degree.

From that time on, Colin produced a succession of significant papers and several influential books—on philosophy, mathematical logic, and probability—building a formidable international reputation as an authority in those areas.

Colin was resolutely independent in his academic work, resisting from the start the LSE’s prevailing orthodoxy handed down by Karl Popper. He showed that much of Popperian philosophy rested on faulty foundations and, at a time when it was deeply unpopular, indeed condemned, in academic circles, he instead pursued a research interest in Bayesian induction, gradually coming to favour a subjective interpretation. Colin and I shared that interest and point of view and we co-authored several papers and a book—Scientific Reasoning: The Bayesian Approach— which, over seventeen years, went through three editions.

Colin became Professor of Logic at LSE in 1997; from 2003 to 2005 he served as President of the British Society for the Philosophy of Science. On retiring from the LSE in 2008, having married the distinguished philosopher of science Margaret (“Margie”) Morrison in 2003, he joined her in Canada and accepted a professorship in the department at the University of Toronto where she was a professor. Margie survived Colin by only a year.

His long publishing career focused mainly on the foundations and applications of probability theory. From at least 1995 he explored supposed justifications of countable additivity, the subject of this, his final paper. He showed that nearly all the justifications are either invalid or beg the question. De Finetti’s case against countable additivity, Colin argued, depends on a view of subjective probability as a species of logic—a view that he propounded in a number of publications.

Colin’s final book, Objecting to God (2011), is a logician’s crusade against what he saw as the illogic and obscurantism in much religious discourse: “There is a profound moral issue,” he wrote, “in the elevation of faith over evidence. Impartial evidence is the defence of honest people against imposters and frauds.”