Comparing the views of Plato, Aristotle,
and Galen on Human Digestion
The unique interpretations of
natural philosophy given by Plato, Aristotle and Galen offer different perspectives on the human anatomy and
physiology. The ancient natural philosophers were concerned with the study of
the structure and function of the human digestive system. Plato, Aristotle,
and Galen in their systematic and empirical inquiries make phenomenological anatomical
and physiological observations. Plato’s views of biology are inspired by is
immediate teacher Socrates. Socrates viewed the human
body as comprising of the body and the soul (Phaedo 277), teachings that Plato
replicated in his posterior analysis in the human
digestive system. Aristotle adopts the perspective of Plato but introduces the
issue of form and matter. In his view, he
integrates subjective description. Galen refined the analysis of the human
digestive system by clarifying on the errors of his predecessors. It is Galen who first brings up the issue of
the different faculties in living things and integrates the issue of nutrition (Galen,
2017, p. 226). The research
establishes that the three philosophers offer divergent but complementary views about the interactions in
the human digestive system.
Digestion is one of the natural
processes whose sole intention and purpose is to ensure that humans survive.
The essay will compare the three philosophers chronologically because of the
complementary nature of their views. First, it is important to look into
Plato’s description of the human digestive system. Plato’s argument was built
on Socrates concept of dualism and the separate existence of the human body and
the soul. The duality as described by Plato is given to humans by the power of
the gods (Plato 70) As argued humans are created with the sense of necessity
planted within them, it is the necessity that elicits the desire to eat and
sensation. Sensation according to Plato created the affections, some of which
are related and particular to the tongue (Plato 100). The affection creates
contraction and dilations in addition to
other sensations that bring about taste. Plato describes the taste as the reaction of the tongue that is
stretched to the heart. In term of its function, he says, “When the muscles
contract and dry out and moist the tongue impinges on soft particles of flesh,
as they melt down and dry, this creates a ‘sour’ taste (Plato, 2006, p. 100).”
For a “tangy” taste the small veins are less rough (Plato, 2006, p. 105).
When the sensation washes of the entire area of the tongue then are names “bitter” while if the parts are less
strong than bitter then the measure is “salty.” The particles or food moves slip down into
the narrow veins proportionate to Earthly paths (Plato, 2006, p. 105).
As he describes there s a separate way for air and for food, food follows the
food path and it slips down the moist hollow channel by being churned along the
Plato argues that the digestive
system is, “part of the larger circuits that are interconnected in the whole
animal, as though bound in a prodigious drive
(Plato, 2006, p. 74).”
In this statement, he views the human
digestive system as a circuitry of interconnected tubes. Like a river,
Plato views the digestive system as a river designed in such a way that “food-supplying wave washes over it and then flows
away (Plato, 2006, p. 74).”
He continues with his statement and says that the affections of the human body produce
an uproar that attacks each other; he describes the action in the digestive
system as a series of attacks and collisions. For example, he says, “one of
them could collide with fire, having met something alien from outside or with a
solid junk of earth or with liquid
gliding of waters (Plato, 2006, p. 74).” Such is the nature of interactions that Plato
associates with the process of digestion inside the human body.
Plato describes the functions and
the activities that take place in the liver and the nature of the liver. He
argued that human have a functional liver which indicates the health of the animal (Plato 56). Plato argues that the liver is lucid when
health but it turns blind and plain when the human is dead or sick. He notes
that there is an organ next to the liver that assists the liver by keeping it
pure and clean. He noted that when impurities are present in the liver then the spleen purifies the impurities and
receives them all (Plato, 2006, p. 108).
Plato describes the spleen as a woven hollow which is usually bloodless.
Clearly, Plato defined the liver plays an
important function in the releasing of the sensational digestive juices that
aid the process of digestion.
Plato further explains that once
the food is in the tubular cavities it, a motion called “sensing” is activated and it is this activation that
food moves along the constantly flowing channels to bring about nutriment. Plato also talks of the coiled
growth of the intestines which plays a major function in the uptake of the
nourishment to the soul. Plato takes time to describe that the coiled nature of
the intestines is structured such that the nourishment cannot pass through
swiftly. In regard to waste food, Plato notes that after nutriment some food
flows contrary to the circuit and as such,
it is shaped up into all sorts of contortions at different intervals (Plato
lecture, slide 31). As noted,
incontinence is as a result of gluttony (Timeous, 73A) which causes people to
use much more food than required. These contortions are completely dissoluble
and cannot hold up together. As such they have
coursed along, he uses the term, “they are coursed irrationally (Plato,
2006, p. 75).” At this point,
Plato describes the end process of digestion in the human body.
Immediately after Plato, his
student Aristotle offers a personalized view of the human digestive system.
Like his predecessor be believed in the duality
of living things but in his perspective living things comprised of form and
matter. His description and view of the digestive system are based on the two concepts. According to
Aristotle, form describes the shape, purpose and the essence why something was
created by the gods. On the other hand, his use of matter was to describe the
composition of things. Aristotle notes that animals have perception and
nutritional potentials and different body parts are suited for different uses (Aristotle,
1997, p. 647). Aristotle looks into the digestive system
subjectively by describing the different parts of the human digestive system.
The start by identifying the mouth and that is attached to another part called
the esophagus which is attached to the windpipe. He then looks into the membrane ligatures and the midriff
which end at the belly.
According to Aristotle’s description, the human belly is a flesh-like an organ
which can stretch in all directions. To illustrate the statement he says, “Man’s Stomach resembles that of a dog (Aristotle,
1997, p. 65) .” In this statement, Aristotle notes that the stomach of
humans is much wider than that of a dog but they are similar in form. He claims
that next to the stomach is the gut which is a twisted organ that is somehow
wide. Aristotle illustrates that “The
lower stomach of humans is like the pig’s” (Aristotle, 1997, p.69) he notes it is wider and towards the posterior, it is thick and short. As argued by
Aristotle it is the upper gut and the lower gut that concocts the food with the
help of natural heat. The stomach gives way to the omentum that he says is attached to the mid stomach and is made up
of fatty membranes. The omentum is
present in all omnivores. The gut is interconnected to the mesentery which as described
by Aristotle is a membranous fatty organ with a network of blood vessels that
absorb nutrition. He notes that “the body will take up the nutrients from
the stomach and the intestines as from a trough (Aristotle, 1997, p. 24).”
He notes that blood is the last part of nutrition and it becomes nourished by
taking up a concoction of a rich diet.
Aristotle just like Plato
acknowledged the structure and function of the liver and its location and
relationship with the spleen. Whereas Plato, described the position of the liver
to be adjacent to the stomach, Aristotle described the liver to be below the diaphragm
on the right and the spleen was adjacent to the left side (Aristotle, 1997, p. 69).
It is clear that both Plato and Aristotle noted that the two organs were
transposed and they did similar functions. They also agreed that the two were
linked to the stomach. However, in terms of description,
Aristotle describes the form of the human liver to be similar to that of the
pig (Aristotle, 1997, p. 69).
He goes ahead to claim that most organisms lack a gallbladder although it is
present in some few animals. On the other hand, Aristotle describes the liver
of a man as round in shape and it resembles that of an ox. Finally, he
acknowledges that the liver just like any other organ is interconnected to a
great blood vessel.
on the other hand, shares a lot of basic beliefs with Plato and Aristotle.
He specifically believed in the Plutonic tri-partite soul and the Aristotelian belief in dissection and the impact of
teleology. Although the cam much later he pioneered and made
significant contributions towards the understanding of the human digestive
system (Galen, 2017, p. 221). Galen’s perspective is more refined as he notes that the human nutrition
faculties comprise of four major
processes namely, Attractive process, retentive process, alternative and propulsive faculties (Galen,
2017, p223) Galen brings a new approach towards the process of digestion by
introducing a process. The attractive
process is the process by which organs exert attachment and attraction to
specific products and materials, for
example, food is attractive to the eyes and it initiates the desire to feed or appetite.
As indicated by Galen, “nature is solicitous and this is purposely for
the animals benefit (Galen, 2017, p. 225).”
The statement means that nature has natural ways of making animals to be
attracted to nourishment.
The retention process is another
faculty that Galen mentions, this faculty is attached to the stomach. Like his predecessors, Galen looks at the stomach not
from a structural perspective but from a functional perspective. Galen says the parts of an animal that ate especially
hollow for a reason are the stomach and the organ called the uterus. He noted
that the retention faculty is usually managed by the senses whilst other parts
of the body. He notes that “for the stomach, it retains food until it has been
fully digested (Galen, 2017, p. 229),”
here Galen is giving the function of the stomach. Galen further reinforces his retention
process through the use of dissection, he
argues that if one fills any animals with any food like I have carried out with
pigs then cuts it open after three or four hours then it is likely that you can
find the food in the stomach. Practically, using dissection Galen is able to
offer proof about the function of the stomach in retention of food. The
functional perspective adopted by Galen is different from the descriptive
approach employed by Plato and Aristotle.
Retention of food in the stomach
initiates a third process which Galen calls alteration, which is the process by
which the stomach and the liver will alter and subdue the food. Alteration of the food changes the substance
of the food into nutriment substance for the blood (Galen, 2017, p. 248).
The stomach follows through the
digestion to make the food suitable for other organs. Each of the organs in the body draws nutriment
alongside it and devours the useful fluids until the organism is satisfied. If
satisfied the excess nutriment is stored
up for assimilation. The process is different from what happens in the mouth
where the food is transformed into a new form but it is not completely altered for
nourishment. After nourishment, the food
is saturated with fluid and other food and becomes a burden and thus the
stomach has to get rid of the excess. As reported, the excess food is turned
downwards passing through the length of the intestine and becomes presented for
In summary, the views of Plato, Aristotle, and Galen on the structure and
function of the human digestive system are divergent but complimentary. The complementary
nature of the views is evident when analyzing the scope and the influence of
the philosophers on one another. Plato offers a conceptual framework for the process of digestion in
humans. Then Aristotle gives the order names of the organs involved in the
process of digestion. Galen compliments both Plato and Aristotle by describing
the entire human digestion process accurately. Divergent views come from their
different approaches towards understanding the nature and teleological
relationship. The three have different beliefs and it is their beliefs which
influenced their descriptions.