Principle of inertia

Principle of inertia (political physics)
A principle of inertia stylized type of political physics humor, in reference to Newt Gingrich’s motivations and driving forces, which, according to Chan Lowe (2012), are self-aggrandizement and satisfaction. (Ѻ)
In science, principle of inertia, or sometimes called "Galileo's principle", is the view that in nature there are two states of existence of position of bodies: being at rest or moving uniformly, which are to be treated as being the same. [1] The principle of inertia implies, said another way, that a body moving on a frictionless level surface will continue in the same direction forever at a constant speed unless disturbed.

In 322BC, Aristotle outlined a now defunct precursor model that impressed force (vis impressa), or some other deus ex machina, was needed to ensure that motion is conserved.

In c.530, John Philoponus, in his rejection of Aristotle’s theories of motions, introduced some type of impetus theory, which influenced: Avicenna, Bonaventure, John Buridan (or Jean Buridan), and Galileo, the latter of whom, in his The Two New Sciences (1638), cites Philoponus.

In c.1500, Italian polymath Leonardo Da Vinci, in one of the notes of his Codex Atlanticus (1478-1519), outlined the principle of inertia as follows: [4]

“Every motion will keep its course rectilinearly as long as the nature of the violence impressed by its motor will last in it.”

Da Vinci does not say, however, say whether such ‘impulse’ [violenzia] dies out by itself, or by the action of external resisting forces.

In 1585, Giovanni Battista Benedetti was more explicit on the issue, and discussed the persistence of the speed of a body, even when the causes that have produced that speed to come to an end—and to assign to the force the rule of giving rise to acceleration.

In c.1600, Italian physicist Galileo Galilei (1564-1642) is said to have read and been inspired by Benedetti’s work and to have went on to expand on it into the formulation of the principle of inertia, namely that a body, once set in motion, maintains its velocity if the resultant of the forces applied to it—both acting and resisting (typically friction)—is zero. Galileo is said to have derived this principle by his studies of balls rolling down and then up again inclined planes, expanded to infinity.

Galileo’s inertia model, supposedly, overthrew the older impressed force model of Aristotle.

In 1687, Isaac Newton, in his Principia, stated the principle of inertia as follows:

"The vis insita, or innate force of matter, is a power of resisting by which every body, as much as in it lies, endeavors to preserve its present state, whether it be of rest or of moving uniformly forward in a straight line."

"Unless acted upon by a net unbalanced force, an object will maintain a constant velocity."


In psychodynamics, the principle of inertia, or “Freud’s principle of inertia”, is a tendency for the leveling of excitation to be reduced to zero. [2] The principle of inertia, in the view of English developmental psychologist John Bowlby, seems to trace to Austrian psychologist Sigmund Freud’s 1915 publication “Instincts and their Vicissitudes”, where Freud states: [3]

“By the pressure of an instinct, we understand its motor factor the amount of force or the measure of the demand for work which it represents. The aim of an instinct is in every instance satisfaction, which can only be obtained by removing the state of the stimulation at the source of … the object of an instinct is the thing in regard to which or through which the instinct is able to achieve its aim.”


1. Gleick, James. (2003). Isaac Newton (pgs. 129-30). Vintage Books.
2. Bowlby, John (1999). Attachment and Loss: Vol I, 2nd Ed. (pgs. 22-23). Basic Books.
3. Freud, Sigmund. (1915). “Instincts and their Vicissitudes.” Standard Edition of The Complete Psychological Works of Sigmund Freud, Vol. 14. London: Hogarth Press Ltd.
4. (a) Galilee, Galileo, Frova, Andrea, Marenzana, Mariapiera. (2006). Thus Spoke Galileo: the Great Scientist’s Ideas and Their Relevance to the Present Day (pg. 60). Oxford University Press.
(b) Codex Atlanticus – Wikipedia.
5. Benedetti, Giovanni B. (1585). A Book on Different Speculations on Mathematics and Physics (Diversarum Speculationum Mathematicarum et Physicarum Liber). Turin.

External links
Inertia – Wikipedia.
Theory of impetus – Wikipedia.

TDics icon ns

More pages