Intellectual property law dictates that there can only be one patent per invention, and this patent can only remain in effect for a limited time. However, patent holders sometimes try to avoid this restriction by patenting a similar invention to the previously claimed art under the guise of being a new invention. In the pharmaceutical industry, the courts avoid this problem through the general requirement of nonobviousness, which is the prohibition against patenting an item that is obvious in light of existing knowledge on the subject. The Federal Circuit and the United States Supreme Court differ in their applications of nonobviousness, resulting in a complicated standard. Nonobviousness is a central concept in obviousness-type double patenting, which is a prohibition of patenting something that is too similar to a previoulys patented item. Eli Lilly and Co. v. Teva Parenteral Medicines, Inc., illustrates that, in the motivational aspect of nonobviousness, the Federal Circuit has moved beyond mere motivation.