Though Aristotle differentiated the forms of reasoning that are valid for logic and philosophy from the more general ones that are used in everyday life (see dialectics and rhetoric), 20th century philosophers mainly concentrated on deductive reasoning. At the end of the 19th century, logic texts would typically survey both demonstrative and non-demonstrative reasoning, often giving more space to the latter. However, after the blossoming of mathematical logic at the hands of Bertrand Russell, Alfred North Whitehead and Willard van Orman Quine, latter-20th century logic texts paid little attention to the non-deductive modes of inference.