Recent times have seen a plague of Aristotle bashing basically accusing him of having held up the progress of science. I’m not sure if this started with Steven Weinberg’s book To Explain the World: The Discovery of Science but its publication and the interviews he gave, in which he forcibly expressed one or other version of this idea, certainly increased the occurrence of this accusation. Recently I stumble across a particular concise and trenchant version and I thought it might be instructive, as a historian of science, to analyse its core claim. As I hope to demonstrate only somebody totally ignorant of Western history could possible claim as, the splendidly named, Fuck Em Up Squanto (@Bro_Pair) did, on Twitter, that:

Aristotle was so smart it took world civilization 2000 years to recover from his disastrous physics ideas

First we need to get his time frame turned into concrete dates. According to Wikipedia, Aristotle lived from 384 to 322 BCE so following his death 2000 years would bring us to 1678 CE. Now most people who believe in a Scientific Revolution would date its commencement, and thus the overthrow of Aristotle’s stranglehold, somewhat earlier. Conventional wisdom dates its start to 1543 and the publication of Copernicus’ De Revolutionibus and Vesalius’ De fabrica. More recently David Wootton was touting the nova of 1572 as kick off point. Let us agree on a compromise date of 1600 CE so we have a claim that Aristotle singlehandedly prevented the invention or discovery (take you pick according to your personal philosophy of science) of physics from 322 BCE until 1600 CE.

The first problem is what exactly Fuck Em Up Squanto means by physics. For Aristotle physics was the study of nature and included much that we would now file under natural history but I assume our intrepid tweeter means something approximating to our modern definition of physics and I shall proceed on this assumption. Aristotle contributed thoughts to three major areas that could today be considered parts of physics, astronomy, optics and dynamics. We will briefly look at each of these and its acceptance in antiquity before marching forward through history to the seventeenth century.

In astronomy Aristotle took over and modified the homocentric theories of Eudoxus. Basically a geocentric model using nested spheres to try and reproduce the real movements of the planets and this was already superceded in antiquity, in the second century CE, by the epicycle and deferent models of Ptolemaeus, although much of Aristotle’s cosmology was, at least nominally, retained, of which more later. This means that any (as we will see, misplaced) blame for Greek astronomy should be addressed to Ptolemaeus and not Aristotle.

In optics we actually have a very interesting situation. Amongst the Greeks there are several competing models to explain sight of which one is Aristotle’s. What is interesting here is that Aristotle’s model is a so-called mediumistic one, that is a connection is built up between the eye and the seen object through the medium of the light and the air and the information that constitutes seeing is transmitted to the eye by vibration. This bears a strong resemblance to the wave theory of light developed by Hooke and Huygens in the seventeenth century. In fact some historians of optics go so far as to see Aristotle as a precursor of his seventeenth century colleges. I personally think this is a step too far but at least one cannot accuse Aristotle of stopping the development of modern physics in the field of optics, rather he was ahead of his times. Actually in the optics competition in antiquity Aristotle’s theory didn’t find many takers, the geometric intromission theories of Euclid, Heron and Ptolemy mostly making the running. Again, nothing to blame Aristotle with here.

It is of course in the field of dynamics, the theory of motion, that we will find to true cause of complaint because it is exactly here that Galileo, Newton et al made the great strides that people hail as the scientific revolution, Galileo’s laws of fall and Newton’s laws of motion. So let us examine Aristotle’s theories and their progress through the two thousand years that separate him from the good old Isaac.

Aristotle’s theories of motion seem rather strange when viewed from a modern standpoint. Firstly he regarded motion as just one form of change, change of place. Other forms of change were growth and decay for example. Considering change just for itself he thought it could be divided into natural motion and violent motion. Natural motion was fall on the earth and the motion of the celestial bodies. Celestial bodies moved naturally in circles, a theory he took over from Empedocles, as did most Greek philosophers. Aristotle’s homocentric astronomy of nested spheres functioned like a giant friction drive system with each sphere driving the sphere inside it. Only the outer most sphere needed a driver, Aristotle’s unmoved mover. On the earth, things dropped fell to the earth because they were returning to their natural place. Implying some sort of low-level animism.

All forms of violent, that is non-natural, motion require a mover, which is where Aristotle’s problems start. Why does something that is thrown continue to move once it has left the throwing hand? Aristotle came up with an explanation of the air opening up in front of the thrown object and closing behind it continue to push the object. He was never very happy with his own solution.

On fall modern commentators tend to mock Aristotle because he said heavy objects fall faster than light ones. Because of Galileo we know better! But we don’t. Galileo’s laws of fall are valid for objects falling in a vacuum. Aristotle’s claims are based on observation in the real world. In fact if you formalise Aristotle’s thoughts on fall, what comes out is very close to Stokes’ laws for fall in a viscous fluid. Air is a viscous fluid.

Aristotle’s theories of motion were not all dominant in antiquity but where just the views of one school of philosophy amongst several. In fact in later antiquity the physics of the Stoics was far more prevalent that that of Aristotle. Around the end of the second century CE Romano-Hellenistic society and culture went into decline and eventually total collapse and with it all forms of intellectual endeavour in Europe. Talk of 2000 years of Aristotelian blockage of science becomes simply ridiculous.

A revival of Greek knowledge began in the Islamic Empire in the eighth century CE. Aristotle’s works were known to the Islamic scholars and highly respected but one cannot speak of any form of total dominance or hindrance of the development of science. The Islamic Empire saw advances in mathematics, medicine, engineering, optics and astronomy.

Around one thousand CE Europe started to again develop an urban civilisation and a thirst for knowledge. In the eleventh and twelfth centuries the so-called translators brought translations into Latin of both the ancient Greek and the more recent Arabic knowledge. At first the Catholic Church, the main centre of learning, was wary of what they saw as heathen knowledge and it was first in the latter part of the thirteenth century that Albertus Magnus and Thomas Aquinas created an acceptable melange of Christian theology and Aristotelian philosophy. Particularly appealing was Aristotle’s unmoved mover whom the equated with the Christian God. It is this that people like Fuck Em Up Squanto are referencing with their objections to Aristotle. However we are now talking about the period thirteen hundred to sixteen hundred that is three hundred not two thousand years! But even here we have to be very careful of our criticism of Aristotle.

As Edward Grant, expert historian of medieval science and religion, quipped (medieval) Aristotelian philosophy was not Aristotle’s philosophy. That is the compromise that Albertus Magnus and Thomas Aquinas created between Christian theology and what the considered to be Aristotelian philosophy differed considerably from the philosophy that Aristotle presented in the fourth century BCE. Another point that Grant makes is that it’s very difficult to actually say what Aristotelian philosophy was as it changes constantly throughout the High Middle Ages. That Aristotelian Philosophy was some sort of unchanging, unchangeable monster cast in concrete by the Catholic Church with an injunction against all forms of inquiry is a myth perpetuated by people who believe in the Draper-White hypothesis of an eternal war between science and religion.

Let us look at a specific example of that process of change; in fact an area that would play a central role in the creation of modern science in the Early modern period, the laws of motion. Already in the sixth century CE John Philoponus criticised Aristotle theory of motion and introduced the concept of impetus. This stated that the thrower imparted a motive force to the thrown object, impetus, which decreases over time till the object stops moving. Via the Islamic thinker Nur ad-Din al-Bitruji in the twelfth century the theory was taken up and elaborated by Jean Buridan in the fourteenth century and through him entered mainstream Medieval thought. The theory of impetus played a central role in the early considerations of both Giambattista Benedetti and Galileo who developed the modern laws of fall. The seventeenth-century theory of inertia, Newton’s first law of motion is in reality a consequent development of the theory of impetus.

Also in the fourteenth century the so-called Oxford Calculatores developed mathematical quantified version of Aristotle’s theories, in particular deriving the mean speed theorem, which lies at the heart of the laws of fall. The Paris physicists took up this work and produced graphical representations of the mean speed theorem identical to the ones presented later by Galileo. To quote historian of mathematics, Clifford Truesdall:

The now published sources prove to us, beyond contention, that the main kinematical properties of uniform accelerated motion, still attributed to Galileo by the physics texts, were discovered and proved by scholars of Merton college…. In principle, the qualities of Greek physics were replaced, at least for motions, by the numerical quantities that have ruled Western science ever since. The work was quickly diffused into France, Italy, and other parts of Europe. Almost immediately, Giovanni di Casale and Nicole Oresme found how to represent the results by geometrical graphs, introducing the connection between geometry and the physical world that became a second characteristic habit of Western thought …

These are medieval scholars working within the Aristotelian tradition not blocking science but furthering it.

The optics that the scholastics inherited from the Islamic Empire was that of Ibn al-Haytham, introduced into Europe in the thirteenth century by Roger Bacon, John Peckham and Witelo, and not that of Aristotle. This European version of al-Haytham’s optics laid the basis on which Kepler and others developed modern optics in the seventeenth century. This optics formed a central part of the medieval university science curriculum, no obstruction from Aristotle here.

As already stated above the geocentric astronomy inherited by the medieval universities was that of Ptolemaeus and not Aristotle’s. On the whole during the period leading up to Copernicus whenever Ptolemaic astronomy clashed with Aristotelian cosmology, the astronomers had little problem abandoning Aristotle’s thought in favour of mathematical observation. The period between fourteen hundred and sixteenth hundred saw a steady modification and improvement in Ptolemaic astronomy. Copernicus’ work was part of a general programme of improvement and not some sort of rebellion against an unchanging or unchangeable orthodoxy. That Copernicus’ ideas were not accepted immediately lies in their inherent scientific problems and not some sort of rejection for being heterodox.

Although the above is fairly superficial I hope that I have made clear that the claim that Aristotle’s ideas were detrimental for the development of science for two thousand years in quite simply historical rubbish.