The inventive step and non-obviousness reflect a general patentability requirement present in most patent laws, according to which an invention should be sufficiently inventive—i.e., non-obvious—in order to be patented. In other words, "[the] nonobviousness principle asks whether the invention is an adequate distance beyond or above the state of the art".

The expression "inventive step" is used in European Patent Convention and in Patent Cooperation Treaty, while the expression "non-obviousness" is predominantly used in United States patent law. The expression "inventiveness" is sometimes used as well. Although the basic principle is roughly the same, the assessment of the inventive step and non-obviousness varies from one country to another. For instance, the practice of the European Patent Office (EPO) differs from the practice in the United Kingdom.

The purpose of the inventive step, or non-obviousness, requirement is to avoid granting patents for inventions which only follow from "normal product design and development", to achieve a proper balance between the incentive provided by the patent system, namely encouraging innovation, and its social cost, namely conferring temporary monopolies. In the US patent law, quid pro quo expression is used to justify the need for the non-obviousness requirement.

The non-obviousness bar is thus a measure of what society accepts as a valuable discovery. Additional reasons for the non-obviousness requirement are providing incentives for fundamental research rather than for "incremental improvements", and minimizing the "proliferation of economically insignificant patents that are expensive to search and to license".

According to the inducement theory, "if an idea is so obvious that people in the field would develop it without much effort, then the incentives provided by the patent system may be unnecessary to generate the idea". Thus, there is a need "to develop some means of weeding out those inventions which would not be disclosed or devised but for the inducement of a patent." Merges and Duffy regret that "the inducement standard was not influential in the legal doctrine, and its absence from subsequent case law raises one of the great unanswered questions of patent law: How can courts continue to ignore a seemingly reasonable and theoretically solid approach to determining patentability?"

While trying to weed out the "easy" inventions, the non-obviousness requirement brings in several downsides to the overall patent system, particularly in the pharmaceutical field, which depends on patent protection most heavily. For example,

Although all countries with actively functional patent systems currently have a requirement for inventive step, the need for such a doctrine has been questioned. For example, "substantial novelty" has been proposed as an alternative approach. Also, many countries have, in addition to patents, utility models, which have a lower (or none) requirement for non-obviousness in return for a shorter monopoly term duration. The availability of utility model protection minimizes for inventors, developers and manufacturers the risk associated with the uncertainty of non-obviousness analysis (litigation) outcome (see below).

In the US, there is no gradation stronger inventive step - longer patent duration, and all-or-nothing approach is used. Under such a system, drawing the line between inventive(all) and obvious (nothing) is ambiguous, as numerous lawsuits with changing outcomes on appeal illustrate (e.g. Sanofi-Aventis GmbH v. Glenmark Pharmaceuticals, 748 F. 3d 1354 (Fed. Circuit 2014)). Also, unique to the United States is the possibility to introduce as the evidence of non/obviousness facts, discovered after filing the patent application in question. (e.g. Knoll Pharm. Co. v Teva Pharm. USA, Inc. 367 F.3d 1381, 1385(Fed. Circ.2004) and Genetics Inst., LLC v. Novartis Vaccines & Diagnostics, Inc. 655 F.3d 1291, 1307 (Fed.Circ.2011), In re Khelgatian 53 CCPA 1441, 364 F.2d 870, 876 (1966)).