Today the Feynman Lectures are considered by many to be the best introductory set of lectures on physics ever written. Feynman himself, however, stated in his original preface that he was "pessimistic" with regard to the success with which he reached all of his students. The Feynman lectures were written "to maintain the interest of very enthusiastic and rather smart students coming out of high schools and into CalTech." Feynman was targeting the lectures to students who, "at the end of two years of our previous course, [were] very discouraged because there were really very few grand, new, modern ideas presented to them." As a result, some physics students find the lectures more valuable after they obtain a good grasp of physics by studying more traditional texts. Many professional physicists refer to the lectures at various points in their careers to refresh their minds with regard to basic principles.