What is the teaching-suggestion-motivation (TSM) test?
The teaching-suggestion-motivation (TSM) test is a framework used in patent prosecution and litigation to determine whether it would have been obvious to combine two or more prior art references to arrive at a claimed invention. Understanding it matters because most obviousness rejections under 35 U.S.C. 103 involve combining references, and TSM is the principal analytical tool for deciding whether that combination is legally justified.
The statutory backdrop
A patent for a claimed invention may not be obtained if the differences between the claimed invention and the prior art are such that the claimed invention as a whole would have been obvious before the effective filing date to a person having ordinary skill in the art.
The Supreme Court established the operative framework for that analysis in Graham v. John Deere Co., 383 U.S. 1 (1966). The four-factor Graham analysis covers: (1) scope and content of prior art, (2) differences between the claimed invention and the prior art, (3) level of ordinary skill in the pertinent art, and (4) secondary considerations such as commercial success and long-felt need. All obviousness analysis, including the TSM test, operates within this framework.
What the TSM test asks
The TSM test holds that a patent claim is only proved obvious if some motivation or suggestion to combine the prior art teachings can be found in the prior art, the nature of the problem, or the knowledge of a person having ordinary skill in the art.
The Federal Circuit developed the TSM test to resolve the question of obviousness with more uniformity and consistency in patent examination. It addressed a practical risk: when an examiner already knows the applicant's claimed invention and then searches for prior art references, there is a temptation to assemble those references into the claimed combination using knowledge the examiner took from the application itself, rather than from what the art would have actually suggested to a practitioner at the time. TSM required that a reason to combine exist in the record before combining was called obvious.
Under the TSM framework, the teaching, suggestion, or motivation to combine may come from three sources: the prior art references themselves, the nature of the problem being solved, or the knowledge of a person having ordinary skill in the art.
The Federal Circuit's rigid pre-KSR application
Before the Supreme Court's 2007 ruling, the Federal Circuit treated TSM as a near-mandatory prerequisite: an examiner had to point to explicit record evidence of a teaching or suggestion to combine before the combination could be called obvious. If no prior art document expressly prompted the combination, the combination was often found non-obvious regardless of how straightforward it appeared in context.
This produced a predictable strategic problem. Inventors could patent combinations of fully known elements simply because no reference said "combine these." The test was criticized for creating a formalistic shield against obviousness rather than serving the underlying policy goal of keeping the obvious out of the patent system.
KSR International Co. v. Teleflex Inc. (2007)
In KSR International Co. v. Teleflex Inc., 550 U.S. 398 (2007), the Supreme Court held that the Federal Circuit applied the TSM test too rigidly and that its formalistic application was incompatible with the expansive and flexible approach required by the Graham framework.
The Court identified three key errors in the Federal Circuit's approach:
Narrow problem focus. The Federal Circuit required that prior art elements be designed to solve the same specific problem the patentee addressed, restricting analysis to the problem the patentee was trying to solve. The Supreme Court held that this was wrong: a person of ordinary skill would consider the full field of relevant prior art, not just references aimed at the identical problem.
Limited prior art consideration. The Federal Circuit assumed that a person of ordinary skill would only consult prior art elements designed to solve the same problem, ignoring that familiar items may have obvious uses beyond their primary purposes. This artificially narrowed the pool of prior art that could inform an obviousness analysis.
Rejection of obvious to try. The Federal Circuit concluded that a patent claim cannot be proved obvious merely by showing that combining elements was obvious to try, even when a finite number of predictable solutions existed. The Supreme Court rejected this categorical rule.
Despite the critique, the Court did not abolish TSM. The Supreme Court in KSR held that there is no necessary inconsistency between the idea underlying the TSM test and the Graham analysis, and that TSM remains one valid rationale for obviousness. The Court acknowledged that the TSM test captured a helpful insight: a patent composed of several elements is not proved obvious merely by demonstrating that each element was, independently, known in the prior art. The problem was not the insight, but its rigid application.
TSM post-KSR: one rationale among seven
Post-KSR, the USPTO recognizes seven rationales that can support an obviousness rejection under 35 USC 103, with TSM appearing as Rationale G. The other six are:
| Rationale | Summary |
|---|---|
| A | Combining known elements by known methods yields predictable results |
| B | Simple substitution of one known element for another yields predictable results |
| C | Using a known technique to improve a similar device in the same way |
| D | Applying a known technique to a device ready for improvement with predictable results |
| E | Obvious to try: finite, identifiable, predictable solutions exist |
| F | Known work in one field prompts predictable variations based on design incentives or market forces |
| G | Teaching, suggestion, or motivation to modify or combine references |
The broader set of rationales matters because KSR made clear that examiners should not conclude a combination is non-obvious simply because a TSM-based rationale cannot be constructed. Any of the seven rationales, or a combination of them, can support an obviousness conclusion.
Post-KSR, the motivation to combine prior art references may be implicit and need not appear explicitly in the prior art documents themselves; it may come from design incentives, market forces, or the nature of the problem. Examiners may also invoke common sense as a basis for an obviousness conclusion, provided they articulate the reason and do not rely on conclusory generalizations.
Examiner obligations when invoking TSM
Examiners invoking any obviousness rationale, including TSM, must provide articulated reasoning with some rational underpinning; rejections cannot rest on mere conclusory statements. A properly articulated TSM-based rejection must identify the specific prior art elements being combined, explain why a person of ordinary skill would have had a reason to combine them, and explain why the claimed result would have been predictable.
An office action that simply lists two references and asserts they would be "obvious to combine" without further explanation does not meet this standard. That gap is often the first place a practitioner should look when evaluating an obviousness rejection.
Responding to a TSM-based rejection
Challenge the motivation. If the examiner's reasoning is bare or conclusory, traverse it directly. Pointing out that the office action lacks "articulated reasoning with some rational underpinning" is a legitimate and frequently effective argument.
Demonstrate teaching away. A primary rebuttal to a TSM-based obviousness rejection is demonstrating that the prior art teaches away from the proposed combination, meaning the references discourage or warn against it. Teaching away is particularly powerful because TSM analysis asks what the prior art would have led a skilled artisan to do; if references actively steer away from the combination, the TSM premise collapses.
Show unexpected results. Applicants may rebut a TSM-based obviousness rejection by demonstrating that the combination yields unexpected or unpredictable results. Unexpected results undercut the predictability premise underlying most TSM-style rationales, particularly Rationales A through D.
Present secondary considerations. Commercial success, long-felt but unmet need, and failure of others can rebut a prima facie case. The evidence must have a nexus to the specifically claimed features, not to unrelated business advantages.
Practical notes for prosecution
Pre-KSR, it was often enough to point out that no single prior art reference expressly suggested the combination. That argument is much weaker after KSR, because examiners can now ground TSM in common sense, market incentives, or the nature of the problem rather than in explicit reference language. A substantive response to a post-KSR TSM rejection requires factual engagement with each piece of prior art cited, argument about why a skilled artisan would not have made the combination (or would have faced technical obstacles), and, when available, declaration evidence on unexpected results or teaching away.
TSM analysis also features heavily in inter partes review (IPR) proceedings, where petitioners regularly argue that a patent's claims are invalid as obvious by combining references. The same doctrinal rules govern, but the burden structure differs: in IPR the petitioner must demonstrate unpatentability by a preponderance of the evidence, and the patent owner may respond with secondary-consideration evidence to rebut that showing.