---
title: "Physics (Aristotle)"
chunk: 3/4
source: "https://en.wikipedia.org/wiki/Physics_(Aristotle)"
category: "reference"
tags: "science, encyclopedia"
date_saved: "2026-05-05T03:40:04.675125+00:00"
instance: "kb-cron"
---

=== Book VII (Η; 241a25–250b7) ===
Book VII briefly deals with the relationship of the moved to his mover, which Aristotle describes in substantial divergence with Plato's theory of the soul as capable of setting itself in motion (Laws book X, Phaedrus, Phaedo).  Everything which moves is moved by another. He then tries to correlate the species of motion and their speeds, with the local change (locomotion, phorà) as the most fundamental to which the others can be reduced.
Book VII.1-3 also exist in an alternative version, not included in the Bekker edition.

=== Book VIII (Θ; 250a14–267b26) ===
Book VIII (which occupies almost a fourth of the entire Physics, and probably constituted originally an independent course of lessons) discusses two main topics, though with a wide deployment of arguments: the time limits of the universe, and the existence of a Prime Mover — eternal, indivisible, without parts and without magnitude. Isn't the universe eternal, has it had a beginning, will it ever end? Aristotle's response, as a Greek, could hardly be affirmative, never having been told of a creatio ex nihilo, but he also has philosophical reasons for denying that motion had not always existed, on the grounds of the theory presented in the earlier books of the Physics. Eternity of motion is also confirmed by the existence of a substance which is different from all the others in lacking matter; being pure form, it is also in an eternal actuality, not being imperfect in any respect; hence needing not to move. This is demonstrated by describing the celestial bodies thus: the first things to be moved must undergo an infinite, single and continuous movement, that is, circular. This is not caused by any contact but (integrating the view contained in the Metaphysics, bk. XII) by love and aspiration.

== Significance to philosophy and science in the modern world ==
The works of Aristotle are typically influential to the development of Western science and philosophy. The citations below are not given as any sort of final modern judgement on the interpretation and significance of Aristotle, but are only the notable views of some moderns.

=== Heidegger ===
Martin Heidegger writes:

 The Physics is a lecture in which he seeks to determine beings that arise on their own, τὰ φύσει ὄντα, with regard to their being. Aristotelian "physics" is different from what we mean today by this word, not only to the extent that it belongs to antiquity whereas the modern physical sciences belong to modernity, rather above all it is different by virtue of the fact that Aristotle's "physics" is philosophy, whereas modern physics is a positive science that presupposes a philosophy.... This book determines the warp and woof of the whole of Western thinking, even at that place where it, as modern thinking, appears to think at odds with ancient thinking. But opposition is invariably comprised of a decisive, and often even perilous, dependence. Without Aristotle's Physics there would have been no Galileo.

=== Russell ===
Bertrand Russell says of Physics and On the Heavens (which he believed was a continuation of Physics) that they were:

 ...extremely influential, and dominated science until the time of Galileo ... The historian of philosophy, accordingly, must study them, in spite of the fact that hardly a sentence in either can be accepted in the light of modern science.

=== Rovelli ===
Italian theoretical physicist Carlo Rovelli considers Aristotle's physics as a correct and non-intuitive special case of Newtonian physics for the motion of matter in fluid after it has reached terminal velocity (steady state). His theory disregards the initial phase of acceleration, which is too short to be observed by the naked eye. Galileo's inclined plane experiment bypasses the issue, as it slows down acceleration enough to allow observing the initial phase of acceleration by the naked eye.
The five elements explain forms of observed motions. Ether explains circular motion in the sky, earth and water explains downward motion, and fire and air explains upward motion. To explain downward motion, instead of postulating one element, he proposed two, because wood moves up in water but down in air, while earth moves down in both water and air. The complex interaction between the 4 elements could explain most of the rising and falling motions of objects with different densities.
The velocity of falling objects is equal to 
  
    
      
        C
        
          
            (
            
              
                W
                ρ
              
            
            )
          
          
            n
          
        
      
    
    {\displaystyle C\left({\frac {W}{\rho }}\right)^{n}}
  
, where 
  
    
      
        W
      
    
    {\displaystyle W}
  
 is the weight of the object, 
  
    
      
        ρ
      
    
    {\displaystyle \rho }
  
 is the density of the surrounding fluid (such as air, fire, or water), 
  
    
      
        n
        >
        0
      
    
    {\displaystyle n>0}
  
 is a constant, and 
  
    
      
        C
      
    
    {\displaystyle C}
  
 is a constant depending on the shape of the object. This is correct for the terminal velocity of falling objects in fluid in a constant gravitational field, in the case where most of the fluid resistance is drag force, 
  
    
      
        ∝
        ρ
        
          v
          
            2
          
        
      
    
    {\displaystyle \propto \rho v^{2}}
  
. In this case, the terminal velocity is 
  
    
      
        C
        
          
            (
            
              
                W
                ρ
              
            
            )
          
          
            1
            
              /
            
            2
          
        
      
    
    {\displaystyle C\left({\frac {W}{\rho }}\right)^{1/2}}
  

== See also ==
History of physics
Horror vacui
Euclid's Elements

== Notes ==

== References ==

== Bibliography ==

=== Recensions of Physics in the ancient Greek ===
A recension is a selection of a specific text for publication. The manuscripts on a given work attributed to Aristotle offer textual variants. One recension makes a selection of one continuous text, but typically gives notes stating the alternative sections of text. Determining which text is to be presented as "original" is a detailed scholarly investigation. The recension is often known by its scholarly editor's name.

=== English translations of the Physics ===
In reverse chronological order: