The interregnum between medieval scholastic logic and modern mathematical logic may be taken as having begun about the middle of the fifteenth century. There is no clear mark of division; the change was a shift away from the characteristic interests of the twelfth to the fifteenth century, with nothing of comparable importance arising to take their place. At the same time, certain less desirable trends in scholastic logic were perpetuated. The result is that formal logic was reduced almost entirely to a very imperfectly presented syllogistic. Medieval influences continued to operate in the early years of the sixteenth century, and medieval authors were still sometimes read in the seventeenth, but by the time that William of Ockham's Summa Logicae was printed at Oxford in 1675, no one had written creatively in the idiom of scholastic logic for many years.

The interregnum...