Despite the limitations of Frege's and Gentzen's analysis of deduction, throughout the twentieth century mathematical logic has been extolled, and the importance of Aristotle's logic downplayed. For example, Russell states that mathematical logic gives thought "wings. It has, in my opinion, introduced the same kind of advance into philosophy as Galileo introduced into physics." On the contrary, Aristotle's "logic put thought in fetters." Thus "any person in the present day who wishes to learn logic will be wasting his time if he reads Aristotle."