On the Past and Future of Natural Philosophy NollWalter 2005 <p>The term "Natural Philosophy" was used from the 17th to the middle of the 19th century for what is now called "Natural Science".</p> <p>About 50 years ago, the term was revived by Clifford Truesdell. I will describe why he revived this term. Here is his description of the meaning of the term: "In modern natural philosophy, the physical concepts themselves are made mathematical at the outset, and mathematics is used to formulate theories". Truesdell provided the leadership that led to the foundation of the Society for Natural Philosophy" in 1963.</p>