On the concept of force

This essay is a reaction to an article by Frank Wilczek entitled “Whence the Force F = ma ? ” in the October 2004 issue of Physics Today and to the letters referring to this article in the August 2005 issue. The letter by Ramamutri Avi refers to a paper of mine, published in 1959, but few people in the physics community seem to be aware of the work on the conceptual mathematical foundations of classical mechanics that I and others have done since then.