The atomic philosophy began with the Greeks and the atomic theory came of age in the 50 years following John Dalton's research. Two views of matter competed among the Greeks and during the 18-19th Centuries. Aristotle, Dalton and Faraday saw matter as continuous with particles in contact while Boyle, Gay-Lussac and Avogadro saw them as dynamic entities separated by space. Dalton's reputation and his continuous view of matter stalled the development of the atomic theory between 1810-60 and the atomic understandings of school and college students also are inhibited by intuitive continuous conceptions of matter. Most students - and a few textbooks - insist that the macroscopic properties of a substance are manifest by isolated atoms and molecules of the substance. This appears to be a source of the alternative framework held by many students. The paper reviews both the historical development of the modern atomic concept and students' alternative theories of matter and particles. The paper argues that there are excellent pedagogical reasons for retracing the history of atomism. The flawed projection of mass properties onto a substance's particles may be lessened by understanding how and why scientists from Newton to Avogadro concluded that matter is composed of dynamic, invisible and indivisible particles.