Logical Psychologism is the view that the non-normative statements made by logicians engaged in their business both are about, and draw their evidence from the examination of, the particular conceivings, assertings, and inferrings of particular persons — a range of facts commonly thought to belong ultimately to the science of psychology alone. This view enjoyed wide acceptance during the last half of the 19 th century, being advocated by such men as John Stuart Mill in England, and Sigwart and Erdmann in Germany. More recently, and due as much to misunderstandings and an unfavorable press as to the essential incredibilities it contains, it has suffered an eclipse which is almost total. A part of the purpose of this paper is to show how this eclipse hinders understanding of what Logic is about.