How do you recognize you have a worthy PhD thesis?

Eric Feron[1]


Many aspiring PhD candidates can be confused about what may constitute a PhD thesis. Most often, they state expectations for themselves that largely exceed what constitutes PhD-worthy work, and when they fail to meet them go in deep sorrow only to be rescued by their advisor. Sometimes too, candidates may err on the side of leniency, considering that their work is “PhD grade”, where it is, in fact, “good work”, that is, something they could have done outside the university framework with a much better pay than the ~$26,000/year they earn as research assistants. These thoughts apply, to a milder extent, to MS candidates who wish to write a thesis. Some of the best works I supervised and read have been MS theses.


PhD contributions may be seen along a few non-exclusive categories, which I detail below. These categories include “cool theorems and new methods”, “cool models and applications”, “beautiful, first-of-a-kind demonstrations”, and “cool engineering ideas”.


Cool theorems and new methods

This category of contribution is defined by a strong mathematical content, punctuated by theorems (or lemmas) throughout the work. Typically, the theorems are there to establish indisputable truths given a set of assumptions or axioms, and they may or may not relate to an immediately important engineering problem. Presumably, engineering-oriented academic units would like to see some connection between the theorem and real-world applications, including new engineering design and analysis methods, but this is not an absolute requirement, although the real-world is filled with particular scenarios that really lend themselves to nice, abstract thinking that make it easier to come up with original “results” quickly. This type of contribution requires a strong sense of abstraction, acquired through advanced training in undergraduate and graduate mathematics, or philosophy.  The kind of introductory courses on these subjects offered to undergraduate students majoring in engineering usually does not constitute a sufficient preparation. The example of a thesis that fits in this category is shown here.


Cool models and predictions from these models

This category includes any model that is extracted from real-world data to fulfill a useful application. Coming up with mathematical (in an extended sense) models of a real-world application is very useful because it often allows other researchers to follow-on with numerical experiments and real-world implementations. Many of my students have used the models contributed by previous students. The most famous models include Einstein’s and Newton’s theories of system dynamics, which are used every day for applications ranging from air bags to Global Positioning Systems. Nice models may range from innovative representations of experimental data to compact mathematical explanations of observed phenomena. Coming up with models requires, however, much attention. First of all, a model must be defined from qualified data, and data is often scarce enough not to be of much value for defining reliable models. Second, the model must be of enough significance: A model designed for an ultra-narrow range of operations may not be of much use and therefore may not constitute a significant enough contribution. An example of such a thesis (well, an article that summarizes the thesis) can be found here.


Beautiful, first-of-a-kind demonstrations

This category of PhD theses is not characterized by objective factors, but rather by the “wow” factor: Beautiful experimental demonstrations of an original, but not necessarily outstanding idea usually belong to this category. PhD candidates who succeed in this category of thesis usually are in great demand by University communication professionals. One of the main challenges of this type of contribution is the necessity to clearly isolate what constitutes the novelty of the demonstration at hand. However, they can sometimes get some hard time from examiners if the technologies supporting the achievement do not contain any novelty. An example of such a thesis is given here.


Cool engineering ideas

This last category encompasses PhD theses that emerged from one, usually simply expressed, patentable engineering idea. While the process driving the analysis of the idea may not be radically new, the idea itself falls outside the range of what is known to mankind. Such ideas drive many people to developing startup companies. Since the contribution of the thesis is the idea itself, it is important that it be, at least in part, that of the PhD candidate.  An example of such a thesis is given here .


Your PhD thesis may also be evaluated along the three following axes:

- Creative vs. executive (here, executive means the thesis is the execution of the ideas expressed by somebody other than the student of his/her immediate research environment. One example is the sponsor providing the central research idea and concepts to the research team.)

- Abstract vs. Experimental.

- Engineering design vs. Engineering science.


Cool theorems and methods are usually abstract.

Cool models and predictions from these models are usually experimental and pertain to engineering science.

Beautiful, first-of-a-kind demonstrations are usually experimental and pertain to engineering design.

Cool engineering ideas usually pertain to engineering design and they are creative.





[1] Dutton-Ducoffe Professor of Aerospace Software Engineering, Georgia Tech