35 U.S.C. 102(f) bars an applicant from attempting to patent subject matter that he or she did not invent. It is imperative that the inventors listed on the application conceived of the invention and either reduced it to practice on their own or had someone reduce it to practice for them. An inventor may adopt ideas from many different sources, but they may not derive the invention from another inventor (or steal it for that matter).

102(f) is fairly self explanatory. However, there is one catch. An application may be rejected under 102(f) even if just one contributing inventor is not listed on the application.  For example, Joe, Bill and Jane (Joe's girlfriend at the time) all partake in conceiving of an idea and reducing it to practice. But Jane dumps Joe. Joe is so mad, he convinces Bill to leave her off the application. If the PTO finds out that Jane was a joint inventor in the subject matter, the application will be barred from gaining a patent.