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Natural Science - Year I

Unit 35: Observation, Induction, and Deduction

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Lecture Outline

Exploration and Science

Bacon (1561-1626) is living in a period of great exploration.

European Voyages

VoyagerNationalityDatesRegion explored
Voyager Nationality Dates Region explored
Prince Henry the Navigator Portugal 1419-1460 West coast of Africa
Christopher Columbus Italian, sailing for Spain 1492 Caribbean and Central America
John Cabot England 1497 Newfoundland (North American mainland)
Vasco de Gama Spanish 1497-98 Sea route to India
Amerigo Vespucci Italian 1499-1502 South America
Ferdinand Magellan Spain 1519-22 Ship circumnavigates the globe (Magellan dies in Philippines)
Francisco Pizarro Spanish 1530 Conquers Incan Empire
John Smith English 1606 Establishes Jamestown in Virginia
Henry Hudson English 1608 Explores New England/Canadian coast and rivers
Abel Tasman Dutch 1642 Australia and New Zealand
James Cook English 1768-1779 South Pacific

The European explorers found many new plants and animals they had never seen before on the European or Asian continents, and they brought to the New World many plants and animals that were not native to North or South America. (Unfortunately, they also brought new diseases, and took American diseases back to Europe). Many of the foods and animals that we associate with particular countries or cultures were not native to those cultures, but were part of this great “Columbian exchange”. As a result of this exchange, the diets and economies of many countries changed radically.

For example, the horse is not native to the Americas. The great horse culture of the Plains Indians that has become iconic in American history didn't exist before 1500. Around that time, Spanish conquistadors brought horses to the Mississippi Valley and Mexico, and those that escaped bred in the wild, were found and tamed by Plains Indian tribes, and by the time of American expansion into its West, the plains Indians were dependent on the horse to hunt buffalo.

Coffee, which had its origin in Africa and Arabia, and sugar cane in Asia, as well as vitus vinifera from France, the grape from which wine is made, all made their way to the New World, and became cash crops for Central and South America. Explorers also brought oranges from Spain and the Middle East to Florida and Brazil, bananas from Africa to Central America, cattle to the plains of Texas and Argentina, and they took pineapples from Brazil to Hawaii.

An example of a plant moving in the other direction, from the New world to Europe and Asia, is the potato, which is native to South America. Because it was well adapted to growing in northern climes as well, it became a staple food in both North America and Europe, where Ireland was so dependent on it that when the potato crop suffered a blight in the 1840s, there was widespread starvation. The corn-like maize and manioc food crops which were grown by New England Indians actually displaced wheat grown in North Africa, and became its most stable food crop.

We now associate the tomato with Italian food and hot peppers with Indian or Thai food, but the tomato is actually related to the potato and part of a group of plants that include chili peppers as well. They were all South American plants, and domesticated by the Aztecs and Incas. European explorers, possibly as early as Columbus and Cortez, took the tomato back to Europe and the chili to Asia. In this particular case, not everyone was ecstatic to find any food to eat. These plants are all part of the same species that includes the deadly nightshade, and many Europeans were reluctant to eat tomatoes, believing them to be poison. There is some circumstantial evidence to support this idea. Wealthy people who used lead-rich pewter forks and spoons would find their food tainted with lead when eating highly acidic foods like grapefruit and tomatoes.

The discovery of these new plants and animals challenged Europeans to find new ways to describe and classify plants and animals. Because these organisms had no history within the European culture, there was no way to study about them from Greek or Latin texts. The only way to learn about them was by direct observation. And this is where Francis Bacon, John Locke, and David Hume become important influences in the history of science: they identified a process of thinking we call imperial system, the view that knowledge comes from experience through the senses.

Take a look at the Google book scan of the Herbal of Pier Andrea Mattioli (1501-1577). He was a commentator on the Materia Medica, the herbal of our old friend Dioscorides, but his work, published around 1554, contained descriptions of plants Dioscorides would never have seen, including the tomato! Scroll through several pages, and note the detailed woodcut illustrations.

Methods of Scientific Analysis

Bacon was well aware that human beings notice things “selectively”, and also remember them selectively. That is why he emphasized through recording of careful, planned observations. If we make a list of everything that we are going to observe, we are less likely to miss something simply because it doesn't fit our expectations, or because we find it was interesting at the time. Following the principles of Bacon's empiricism, we would record as much as possible about a given situation, without reference to a particular theory. Analysis would begin only when we were through with our observations.

Empiricism by itself does not give us knowledge of relationships. Later philosophers added inductive and deductive methods of reasoning as complimentary ways of relating individual facts. Induction helps us to find common characteristics and create classes of objects, but it cannot be used as proof of its conclusion. Deduction allows us to use those characteristics and identify a particular object as a member of a given class, but our conclusions are only as good as the premise we use.

Example of inductive reasoning based on empirical observations

In the late 1500s, as we shall see a few units hence, the Danish astronomer Tycho Brahe closely observed the positions of Mercury Venus and Mars, and kept detailed records. His assistant, Johannes Kepler, used these records after Brahe's death to determine the orbits of these planets. Contrary to his expectations, he found that the orbits were ellipses, not the circles assumed by Aristotle, Ptolemy, and Copernicus. He could not explain why the planets had elliptical orbits, but all the planets he examined did have elliptical orbits. He stated this conclusion as his first law: All planets move in elliptical orbits. This is an example of induction -- it is a generalization reached by looking at several examples and seeing what they had in common. It is not based on any cause-effect analysis. Kepler proposed a second law based on the rate of the planets: the length of the semi-major axis (a) of the ellipse of a planet is related to its period (P): P2 = a3.

Example of deductive reasoning based on empirical observations

In 1781, the English astronomer William Herschel, discovered a new object moving against the background pattern of stars, and concluded that he had discovered a new planet (which he had -- it was Uranus). Based on the rate at which it was moving, Herschel calculated its period (time for one revolution around the sun), and determined the distance to the object using Kepler's law. This is an example of deduction: because the object is a planet, its distance is a function of its period.

Study/Discussion Questions:

Further Study/On Your Own