The church is an authority on knowledge in the Middle Ages. During this period, there are different beliefs compared to modern beliefs; the earth is 6000 years old (1), the man is not an animal (2), the sun revolves around the earth (3), thinking takes place in the immaterial mind (4), the Greeks knew everything (5).

The belief that the Greeks knew everything led to the emphasis on the preservation of knowledge rather than the generation of new knowledge in Europe. However, science flourishes in the Middle East (e.g. mathematics and physics). The Middle East introduced Europe to Aristotle again in the 13^th century. After Aristotle’s rediscovery, his knowledge was presumed to be correct until Galileo refuted some of his knowledge, proving that Aristotle was fallible.

Augustine of Hippo was a scientist from Algeria in the Middle Ages:

• Formulates the first theory on learning.
• Discovers the unconscious
• Identifies the problem of other minds

He introduces the argument from analogy as a solution to the problem of other minds and this problem is still relevant in modern science (e.g. AI research).

In Europe, during the Middle Ages, people believed in the Ptolemaic system, the idea that all celestial bodies orbit around the earth. This is a flawed model as it requires epicycles in order to explain retrograde motion, making this model mathematically complex. The heliocentric model, developed by Copernicus, refers to the idea that all celestial bodies orbit around the sun.

Copernicus published his book promoting the heliocentric model very late because of a fear of the church’s reaction (1) and because of uncertainties about his model (2). There were several objections to Copernicus’ heliocentric model:

• The model does not explain the data very well.
• The model does not explain why entities are not thrown into space if the earth is moving.
• The model does not explain why a stone falls straight down if the earth rotates.
• The model does not explain why the moon is not orbiting the sun.
• The model is mathematically as complex as the Ptolemaic system.

The mechanistic view is the worldview according to which everything in the material universe can be understood as a complicated machine.

Galileo Galilei has several important characteristics:

• Defends the heliocentric model using experiments; he disproves counter-arguments to the heliocentric model.
• Disproves Aristotle on several occasions.
• Recognized the value of experiments; he recognized that artificial conditions provide insight into the natural world.
• Proved the existence of moons at other celestial bodies.
• Recognized the value of using instruments to aid observation.
• Had a conflict with the Roman Catholic Church.

In the Middle Ages, the idea that instruments could be better than the naked eye is revolutionary. The idea. The value of experiments is still relevant in modern science, as there are still discussions about ecological validity. Galileo’s conflict with the church results in house arrest and is the break between religion and science.

Kepler has access to enormous amounts of measurements on the orbits of planets and discovers that planets move in ellipses, rather than circles, simplifying the heliocentric model, making it more plausible.

Bacon has several important characteristics:

• Articulates the scientific method; a combination of reasoning and observation.
• Proposes that people pay attention to deviating observations rather than confirmatory observations.
• Realizes that humans are fallible and states that human psychology interferes with finding the truth (i.e. biases).
• Proposes a normative methodology in order to overcome fallacies.
• Stresses the value of the experiment; he proposes that science should be provocative rather than passive.

Bacon describes several fallacies:

1. Idols of the Tribe
   These are fallacies that all humans commit and are inherent to human nature (e.g. visual illusions, seeing patterns when there is no pattern, seeking confirmation and ignoring refutations).
2. Idols of the Cave
   These are fallacies that humans commit because they are part of a certain culture and have certain interests and habits (e.g. prejudice, stereotypes). These fallacies are things that are believed because a lot of people believe it, rather than due to evidence.
3. Idols of the Marketplace
   These are fallacies that humans commit as the result of language. It is possible that language leads to faulty beliefs as some words do not refer to anything (e.g. believing some things exist because a word refers to it, although it does not; depression exists because there is a word when it is a term for a latent variable).
4. Idols of the Theatre
   These are fallacies humans commit because authorities state that something is true (e.g. something that is on the news must be true).

The fallacies that people make in the Idols of the Marketplace are known as reification; treating an abstraction as if it were a real thing (e.g. latent variables, intelligence). Bacon’s fallacies are still relevant in modern science, as science relies on admitting human deficit, rather than denying it. Bacon’s distrust has been institutionalized by science (e.g. experiment, statistical test).

According to Bacon, theories must be tested against observations because humans are fallible, as demonstrated by the Idols. In his view, good science uses rational inference when constructing theories and derives empirical predictions from them which are then tested in an experiment.

Newton has several important characteristics:

• Introduces the scientific approach in physics.
• Integrates the findings of multiple researchers in one theory.
• Formulates the theory of gravity; this theory is written in mathematical terms and explains a great number of phenomena using simple principles.
• Sets the example for many future researchers in different disciplines, including psychology.

Comte is the founder of positivism and proposes that civilisations pass through three stages:

1. Theocratic stage
   In this stage, gods and spirits dominate the culture. There is a transition from animism to polytheism.
2. Metaphysical stage
   In this stage, philosophical explanations dominate the culture.
3. Positivistic stage
   In this stage, scientific explanations dominate the culture and science becomes the motor of progress.

The scientific revolution has changed the view of nature. The reasons for the scientific revolution are population growth (1), the end of the feudal system (2), the absence of stifling pressure from religion or authority (3), new inventions (4), the existence of universities (5) and the massive enrichment from the Greek and Arab civilizations due to the fall of Constantinople (6).

Science was able to become more important due to the absence of disaster (1), benevolent religion (2) and the establishment of learned societies (3). A disaster would have threatened the (political) stability required for science to thrive.

The counterforces to the rise of science were the Roman Catholic Church (1), the Protestant Church (2), the humanities (3) and the Romantic movement (4). The humanities believed that a society based on reason alone would be a breach with the social tissue on which societies are built. The dichotomy between the Romantic movement and science, on the other hand, was not as extreme as often thought.

Historians’ awareness of the impact of science was hindered because historians are a part of the humanities (1), there was a discussion about whether progress exists in both science and history (e.g. paradigms) (2) and because the accumulation of knowledge felt like a steady process without interesting twists and turns (3).