Critical thinking is an iterative, reflexive process reliant on faculties of reason and formal logic with an end goal of rational decision-making. Via questioning theorized or pre-supposed knowledge in the context of factual evidence, critical thinking promotes deep understanding through skepticism and systematic analysis.  This article demonstrates that a critical thinking mechanism of thought is developed through practice, and is a pivotal aspect in development and personal growth.


Critical thinking pervades the history of all engineering – what may seem
to be an obvious course of events cascading from one to the next can usually be
dissected into various applications of the scientific method, one of many
formal examples critical thinking. Consider the invention of the cavity
magnetron in 1940 – a vital, largely unheard of innovation that resulted in
compact radar machines; a timely invention given the Second World War, and a
seemingly complete one, but strangely before its time[1].

Percy Lebaron Spencer was an electrical engineer working for Raytheon, and
was already well renowned within the company as an innovative mind, having
revolutionized the process of manufacturing their magnetrons. While tinkering
with an active radar set, he noticed that a candy bar in his pocket had melted
– this phenomenon was not necessarily unheard of; others had noticed similar
effects, but Spencer was the first to think critically about it. He
discerned that the ambient heat was not necessarily a result of the thermal
dissipation from ordinary operation, but possibly the effect of targeted
radiation ‘cooking’ the chocolate.  After a great deal of testing,
observation, and optimization, he invented the microwave oven[2].

This is a concrete example of the application of critical thinking, and
provides an important element of context in the analysis this article presents.
By abjectly defining critical thinking and examining examples throughout
history, we can observe its effects on our Senior Design Project, and
development of concepts and ideas in general.  “Automated Plant Care Via Collaborative Hydroponic System” (with Nathan Harada and John Pothier) was our senior Capstone project.  Hydroponics is a method of growing plants through water-based nutrient solutions without soil. This project designed a data model and algorithm to monitor the hydroponic environment of plants to facilitate and optimize their health and growth.  Critical thinking was necessary to construct the growing model of plants for the nutrient delivery system and the machine learning algorithm.  The self-contained system incorporates user observations to care for plants via the Internet. A database stores user feedback and history of control states for data visualization and to provide information to the learning algorithm.  Optimization for machine learning was achieved by utilizing plant state history and growth parameters according to gradient decent algorithm. The application is intended for people in urban settings and confined spaces that desire to growth plants and vegetables.


Defining Critical Thinking

Because critical thinking represents something of a philosophy in addition to a
method, there exist several definitions that convey roughly similar ideas.
Random House Dictionary states that critical thinking is:

“Disciplined thinking that is clear, rational, open-minded, and informed
by evidence.”

This is a concise definition that allows for a broad range of
interpretations, but as the notion itself is open-ended, the definition we will
work with. Disciplined thinking means that the manner of thought is closely
controlled and monitored, while its clarity, rationality, and open-mindedness
imply that the thinking follows rigorous rules of logic that can be explained
simply and succinctly. Finally, information via evidence is the most classical
methodology behind constructing an argument or forming an opinion. By utilizing
these simple ideas, the fundamentals of critical thinking are formed – we can
consider the story of Percy Spencer as an example.

Case Study

Spencer noticed a unique phenomenon – the melting of the chocolate in his pocket from an unknown heat source. As previously noted, he was not the first person to observe this, but his interaction was the first to employ the use of
critical thinking. Firstly, and perhaps most importantly in the context of new
discovery, his thinking was open-minded. Radiation was poorly understood at
best in the 1940’s, with many of the mistakes we made then still being felt
today[3]. That Spencer was willing to attribute this new phenomena to some
unknown aspect of radiation showed that his thinking was open to new ideas
and discoveries, an important part of critical thinking. Secondly, his thinking
was disciplined and informed by evidence. He repeated the experiment with the
same test conditions, and observed and reported on his findings for each event;
with consistency in his results, he was able to draw forth the
rational conclusion that in some way, the magnetron was producing
directed heat. Finally, his thinking was clear. After studying the results, he
determined that the mechanism of dielectric heating was a result of targeted
microwave energy, and was able to clearly express his ideas to his superiors at
Raytheon [2]. The end result was an innovative piece of household technology
that could not have been invented if not for the powers of critical

If this process sounds familiar, it is because the act of thinking
critically falls under many taxonomies – as mentioned previously, among the
more well known appellations is the “Scientific method”.  The scientific
method can be briefly defined in the following four steps[4]:

  1. Observation and description of a phenomenon or group of phenomena.
  2. Formulation of an hypothesis to explain the phenomena.
  3. Use of the hypothesis to predict the existence of other phenomena, or to
    predict quantitatively the results of new observations.
  4. Performance of experimental tests of the predictions by several
    independent experimenters and properly performed experiments.

It stands to reason that these abstract notions of problem solving are, in
their roots, quite similar. The observation, or problem statement, followed by
hypothesis and hypothesis testing, form the foundation of all new knowledge;
and is in itself a formula for synthesizing and cataloging new information.

Learning to Think Critically/Further Applications

David Foster Wallace once wrote that learning how to think, “really means
learning how to exercise some control over how and what you think. It means
being conscious and aware enough to choose what you pay attention to and to
choose how you construct meaning from experience.[5]” This is precisely the
goal of many higher learning institutions: the promotion of critical thinking
via teaching how to learn. Organizations, such as
CriticalThinking.org, exist purely for the sake of designing curriculum around
teaching the basics of thinking critically to students – and the general
consensus remains that critical thinking is among the most high priority
aspects of education offered today [6]. For this reason, it is easy to
understand why the ‘Critical Reading’ section of the SATs is considered one
of the most difficult to score well on, as well as the most important to fully
prepare for: the skills can be learned and developed through practice and
effort, and they are important enough to warrant (until 2007) fifty percent of
the bandwidth of the standardized university entrance exam[7]. The important
advice offered by many of these practice agencies is to train the mind to
follow steps of logic and reason based on evidence – follow the scientific

These tools prove vital to the Urban Hydroponics system in particular,
because the notion is not built upon prior research, but involves a thorough
“ground up” investigation. As such, all research must be done meticulously
and to the standards of academic rigor expected at institutions of higher
learning. Furthermore, all rationales must be logical and consistent with the
rules of critical thinking, such as metrics for plant health, hypotheses for
pump driver controls, and arbitrating feedback.


It stands to reason that the topics discussed in this article can be further
applied to any situation in which rational thought and scientific discovery are
important. Critical thinking can be thought of as a powerful problem-solving
tool, or perhaps even more accurately, as a highly focused lens through which
to few the world. With a large field of view and a versatile aperture, it is
possible to see a great deal and draw powerful conclusions when looking at the
world through the proper filter. In the case of our intelligent hydroponics
system, these skills have previously, and will in the future, prove

All senior design projects, as well as engineering challenges in everyday
life, aim to solve problems using available resources and sound science.
Perhaps the greatest resource available is the ability to think rationally
about a problem and derive viable solutions to them.

Cited References

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