RENAISSANCE

Intro: Although the Renaissance was primarily an artistic and cultural movement, its emphasis on free thinking challenged the authority of religion, and paved the way for an unprecedented age of scientific discovery

Tradition undermined

THE Scientific Revolution began with the publication in 1543 of Nicolaus Copernicus’s De revolutionibus orbium coelestium (On the Revolutions of the Celestial Spheres), which presented evidence contradicting the notion of a geocentric universe. A description of this is given at the end of this article.

That same year, Andreas Vesalius published De humani corporis fabrica (On the Fabric of the Human Body), which overturned many orthodox ideas in anatomy and medicine. What followed was a profound change in the approach to enquiry into the natural world. Conventional wisdom, including the dogma of the Church, was no longer blindly accepted, but challenged. Even the work of Aristotle, who had initiated the idea of natural philosophy based on methodical observation, was subject to scientific scrutiny.

At the forefront of this scientific revolution were philosophers such as Francis Bacon, whose Novum Organum (New Instrument) proposed a new method for the study of natural philosophy – systematically gathering evidence through observation, from which the laws of nature could be inferred. But there was also a new class of thinkers and scientists, including Nicolaus Copernicus, Johannes Kepler, and Galileo Galilei. Galileo challenged dogma more than most by proving that the Earth orbits the Sun, and fell foul of the Church for his efforts.

The discoveries made by these scientists, and the methods they used, laid the foundations for the work of Isaac Newton in the following century, and also influenced philosophers such as Descartes, Spinoza, and Leibniz, who helped to shape the ideas of the Age of Enlightenment.

One Cause Only

Central to Aristotle’s philosophy was the concept of the “four causes” (see article). The new scientific methods of the 16th and 17th centuries rejected these, especially the concept of a “final cause”, or purpose. Instead it was proposed that there are only “efficient causes” in nature – i.e. physical causal triggers. Although this is closer to the modern idea of cause and effect, the idea had first been proposed by the Atomists some 2,000 years earlier (see article).

Laws of nature

The theories of Copernicus and his contemporaries heralded a new era of scientific discovery. Religious authority was undermined, but so too was the orthodox concept of the laws that governed the universe, which were based on Aristotelean cosmology and physics. In this new atmosphere of scientific enquiry, conventional assumptions were replaced with laws of nature derived from empirical evidence of observation and experiment.  

The New Method

Induction

Bacon described a method of scientific enquiry using the process of induction, inferring a general rule from particular instances. For example, the rule that water boils at 100C can be inferred because this is the case in every instance.

Experimentation

Often, it is not enough simply to observe in order to come to a scientific conclusion. The scientific method pioneered by Islamic philosophers involves conducting controlled experiments to get reproducible results.

Galileo Galilei once said: “In science the authority of thousands of opinions is not worth as much as the reasoning of one individual.”

Sunspots – The detailed study of sunspots made by Galileo and others showed that these are inherent features of the Sun. These observations contradicted the Aristotelean idea of the perfection of objects in the heavenly spheres.

Gravity – Although it may only have been a thought experiment, Galileo dropped two balls of different weights from the Tower of Pisa to show that they fell at the same speed. This refuted Aristotle’s assertion that heavy objects fall faster than lighter ones.

Elliptical orbits – Once it was proven that the Earth orbits the Sun, the orbits of the planets could then be explained. Kepler discovered that the orbit of Mars was not circular, but an ellipse, and concluded that all the planets had elliptical orbits.

THE GEOCENTRIC UNIVERSE

Outside the orbit of the Moon lies the celestial region in which the Sun, the planets, and the stars move in orbits at various distances from the Earth. Unlike the sublunary region, the celestial region is made from an incorruptible substance, which Aristotle calls the “quintessence”, or fifth element. According to Aristotle, the natural movement of the earthly elements is up or down, towards or away from the centre of the Earth. By contrast, the natural movement of things in the celestial region is circular. What’s more, earthly elements tend towards a position of rest, while celestial movement is unceasing. Thus, Aristotle reasoned that the stationary Earth, although imperfect, is at the centre of the cosmos.

Beyond the Moon’s orbit, Aristotle identified 55 concentric spheres to which the celestial objects are attached. As they radiate away from the Earth, the outer spheres draw closer towards perfection, stretching into spiritual realms that have no material existence. The universe, for Aristotle, is a perfect form, and cannot have come into being at any one time: it is eternal, unchanging.