The Legacy of Aristotle

Part 3:

BIOLOGY

• These are the remains of Aristotle’s school at Mieza in Macedonia.

• This is the lagoon on the Greek island of Lesbos where Aristotle did much of his research on marine life.

1: Aristotle’s greatest achievements as a scientist are in

biology. He directly studied almost 500 species including

land animals, birds, fish, marine mammals and

cephalopods.

• His discoveries sometimes anticipated modern discoveries:

• (a) Dolphins are sea mammals not fish.• (b) The distinction between homologous and analogous parts.

– homologous: similarity due to shared ancestry e.g. the forelimbs in mammals;

• – analogous: organs that perform a similar function but evolved– separately, e.g. wings of a maple seed an a bird’s wings.

• (c) Some sharks give birth to live young

• (d) Some reef fish transform from female to male• (e) The Eustachian tube linking the middle ear to throat in humans• (f) The embryological development of chickens which he

discovered in one of history’s first recorded experiments.• (g) The mating process of the octopus

• 2: Aristotle set out his program for biological research: (a) we should begin with observational, i.e. empirical evidence before

developing causal explanations for what we see. • (b) he views biological phenomena as examples of final causes; we

must explain parts of animals in terms of their purpose e.g. reproduction, defense, escape. “Everything that nature makes is a means towards an end [goal]” (Parts of Animals, 1,1). He develops a teleological view of biology.

• (c) empirical studies should be divided into (1) getting food; (2) actions; (3) habits; (4) bodily parts; (5) reproduction.

• (d) in classifying kinds of creatures we must recognize “natural groups” on the basis of common (universal) essential attributes. Classifying should not break up “natural groups.”

• (e) in classifying we should start with a large group (genus) of “proximate creatures” that seem generally similar and then identify particular species that fit into the genus

• (f) One important aspect of his systematics was the “scala naturae,” i.e. the scale, ‘ladder,’ or hierarchy of nature. The underlying idea is, once again, that nature is orderly and, in regards to complexity, is arranged in a hierarchy. In general terms, the plant is the least complex and humans are most complex.

• 3. Aristotle’s Taxonomy of Animal Life

This arrangement was not improved until Linnaeus and Cuvier in the 18th C CE.

• BLOODED ANIMALS

– A: Bearing live young (viviparous)

• 1: Man

• 2: others . . . including cetacea (sea mammals)

– B Egg Layers (oviparous)

• 1: with perfect egg: Birds

• 2: scaly reptiles

• 3: with imperfect egg: fish,

– C. NON-BLOODED ANIMALS

– 1: non-shelled soft sea-animals: cephalopods,

– 2: soft-shelled sea animals: crustacea

– 3: Insects

– 4: Bees

– D. VERMIPAROUS (spontaneous generation from slime etc.)

– 1: molluscs

• 2: zoophytes (an animal that looks like a plant); e.g. sea anemone.

• *** Aristotle recognized that there were intermediate species that were hard to classify, e,g. sea anemone.

• *** He recognized that there was adaptation within species to accommodate the needs of the whole organism.

• *** However he believed in the immutability of species, i.e. one species did not change into another since this would require a change of essence. This belief was not successfully challenged until Charles Darwin in the 19th C CE.

• *** Note that for Aristotle, human beings are physically parts of nature like all other kinds of being. Humans are only distin-guished by their rational soul.

• *** According to Aristotle, life is teleological, i.e. develops towards a final cause. Aristotle believes nature works like a physician or builder who “starts by forming for himself a definite picture . . . of his end . . . and this he holds forward as the reason and explanation of each subsequent step that he takes . . .” (PA, 1, 1).

• In this way he connects his theory of biology to his theory of reality in general: four-fold causality holds true for each (material, efficient, formal and final causes).

– (a) Remember: the end, the final cause does not have to be conscious or deliberative; it is implicit in the efficient and formal cause (see Lecture 1). The final cause guides or limits the process of building or development and (usually) prevents it from going wrong or out of control.

– (b) Without such control, each subsequent step would be random, unconstrained or unlimited. Aristotle recognises that such random events sometimes happen in nature when we get spontaneous variations or deformities. There is a limit to the

– control exerted by final causes; sometimes the imperfections of

matter can over-ride final causality.– (c) However, despite (b), in biology, the final causes are usually

more important than efficient causes because the final cause guides the efficient causes to a particular goal or state instead of any possible goal.

– (d) Explanations that do not take the material and formal/final cause into consideration are incomplete and “tell us nothing in reality about nature.” (PA 1, 1). This is because the soul which is the formal and final cause, “constitutes the nature of an animal much more than does its matter” (PA 1, 1).

• Aristotle’s final causes limit the effects a process can have and thus guide the process towards certain ends, goals, states.

• Aristotle made enormous contributions to the development of science and to philosophy of science.

– (a) He pioneered the approach that reality was fundamentally rational, could known and understood by rational and objective procedures and could be demonstrated to be orderly and law-abiding. Reality is not just a play-thing of supernatural forces or ‘gods.’ Without this foundational belief, no science of any kind is possible.

– (b) Although he was wrong on many details (he was right on as many others) he laid the foundation for scientific progress with his belief in the rationality and orderliness of nature. On this issue nothing has change in science and the philosophy of science since Aristotle’s time.

– (c) He pioneered both empirical/inductive studies as well as deductive methods in analysing reality. He firmly put the quest for scientific knowledge on the footing of a quest for knowledge about causes. He showed how reality can by known by means of

correctly used procedures in logical reasoning.

– d) His method of analysing reality by means of such concepts as actuality and potential, essence and attribute, and matter and form is still viable and the subject of intense philosophical debate.

– (e) His concept of four-fold causality and especially final causes is still a controversial issue today in philosophy although science itself has limited itself to what he calls ‘efficient’ causality. What is or is not implicitly entailed in such ‘efficient’ causality is still a matter for philosophical debate.

– (f) Ironically, while his work itself promoted empirical research as well as experimentation (remember Aristotle and the chicken eggs) his work became a hindrance to the development of science because he was venerated too much and took on quasi-religious authority. This corrupt phase of misusing his work began in the 14th C CE and brought about crises in the form of conflict with Copernicus (16th C CE) and Galileo (16th -17th C CE) who disproved his geocentric theory of the universe.

– (g) The lesson we can learn from this ironic development is that we should follow Aristotle’s personal example in seeking new knowledge rather than the example of those who misused his work.

• ASSIGNMENTS ABOUT ARISTOTLE’S BIOLOGY

• (1) Aristotle laid out many guidelines for doing biological research. Identify four of them and explain why in your opinion each of them is or is not useful today.

• Your answer will be marked on how complete and thoughtful your explanations are.

• (2) Thinking question: why do you think Aristotle believed in the spontaneous generation of lower life forms? What observations could have led him to this conclusion? What invention was he lacking to solve this problem?