''De Motu: Sive, de Motus Principio & Natura, et de Causa Communicationis Motuum'' (''On Motion: or The Principle and Nature of Motion and the Cause of the Communication of Motions''), or simply ''De Motu'', is an essay written by

George Berkeley George Berkeley (; 12 March 168514 January 1753) – known as Bishop Berkeley ( Bishop of Cloyne of the Anglican Church of Ireland) – was an Anglo-Irish philosopher whose primary achievement was the advancement of a theory he called "immate ...

and published as a tract in London in 1721. The essay was unsuccessfully submitted for a prize that had been offered by the Royal Academy of Sciences at

Paris Paris () is the capital and most populous city of France, with an estimated population of 2,165,423 residents in 2019 in an area of more than 105 km² (41 sq mi), making it the 30th most densely populated city in the world in 2020. ...

. Berkeley rejected

Sir Isaac Newton Sir Isaac Newton (25 December 1642 – 20 March 1726/27) was an English mathematician, physicist, astronomer, alchemist, theologian, and author (described in his time as a " natural philosopher"), widely recognised as one of the gre ...

absolute Absolute may refer to: Companies * Absolute Entertainment, a video game publisher * Absolute Radio, (formerly Virgin Radio), independent national radio station in the UK * Absolute Software Corporation, specializes in security and data risk manag ...

space Space is the boundless three-dimensional extent in which objects and events have relative position and direction. In classical physics, physical space is often conceived in three linear dimensions, although modern physicists usually con ...

time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, t ...

and

motion In physics, motion is the phenomenon in which an object changes its position with respect to time. Motion is mathematically described in terms of displacement, distance, velocity, acceleration, speed and frame of reference to an observer and mea ...

. With this essay, Berkeley is considered to be the "precursor of

Mach Mach may refer to Mach number, the speed of sound in local conditions. It may also refer to: Computing * Mach (kernel), an operating systems kernel technology * ATI Mach, a 2D GPU chip by ATI * GNU Mach, the microkernel upon which GNU Hurd is bas ...

and

Einstein Albert Einstein ( ; ; 14 March 1879 – 18 April 1955) was a German-born theoretical physicist, widely acknowledged to be one of the greatest and most influential physicists of all time. Einstein is best known for developing the theory ...

" ( Karl Popper).

Concrete and abstract motion

We must pay attention to facts regarding things and their nature, not to words or to someone's authority. The mind should be concerned with particular and

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most ...

things themselves, not with

abstract Abstract may refer to: * ''Abstract'' (album), 1962 album by Joe Harriott * Abstract of title a summary of the documents affecting title to parcel of land * Abstract (law), a summary of a legal document * Abstract (summary), in academic publishi ...

terms. The effects that are felt on our senses should be noticed. The causes of these effects are rationally inferred and are

occult The occult, in the broadest sense, is a category of esoteric supernatural beliefs and practices which generally fall outside the scope of religion and science, encompassing phenomena involving otherworldly agency, such as magic and mysticism ...

qualities.

Gravity In physics, gravity () is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the str ...

and

force A force is an influence that can cause an Physical object, object to change its velocity unless counterbalanced by other forces. The concept of force makes the everyday notion of pushing or pulling mathematically precise. Because the Magnitude ...

are examples of occult qualities. But they can be useful terms. Gravity can designate concrete bodies in motion and force can designate the concrete effort of resisting. However, they should not be used abstractly, separate from concrete, individual things. If no change occurs and there is no effect, then there is no force. Force, gravity, and attraction are

mathematic Mathematics is an area of knowledge that includes the topics of numbers, formulas and related structures, shapes and the spaces in which they are contained, and quantities and their changes. These topics are represented in modern mathematics ...

al,

hypothetical A hypothesis (plural hypotheses) is a proposed explanation for a phenomenon. For a hypothesis to be a scientific hypothesis, the scientific method requires that one can test it. Scientists generally base scientific hypotheses on previous obser ...

abstractions and they are not found in nature as physical qualities. The

parallelogram In Euclidean geometry, a parallelogram is a simple (non- self-intersecting) quadrilateral with two pairs of parallel sides. The opposite or facing sides of a parallelogram are of equal length and the opposite angles of a parallelogram are of eq ...

of composite forces is not a physical quality. It is mathematical. Attempts to explain the cause and origin of motion are abstract and obscure. They are not particular and determinate assertions. Such attempts try to explain the unknown by something that is even more unknown.

Principles or causes of motion

Bodies are not known to contain, within themselves, forces that cause motion.

Mind The mind is the set of faculties responsible for all mental phenomena. Often the term is also identified with the phenomena themselves. These faculties include thought, imagination, memory, will, and sensation. They are responsible for vario ...

s, however, are known to cause motion. Such minds are particular, individual causes that are parts of the primary, universal cause of motion. Bodies are passive, not active. They merely persist indifferently in their states, whether of impelled motion or of rest.

Action Action may refer to: * Action (narrative), a literary mode * Action fiction, a type of genre fiction * Action game, a genre of video game Film * Action film, a genre of film * ''Action'' (1921 film), a film by John Ford * ''Action'' (1980 fil ...

and

reaction Reaction may refer to a process or to a response to an action, event, or exposure: Physics and chemistry *Chemical reaction *Nuclear reaction *Reaction (physics), as defined by Newton's third law * Chain reaction (disambiguation). Biology and me ...

are only mathematical hypotheses, not physical qualities. It is useful to refer to action and reaction when demonstrating mechanics, but they are not causes of motion. We personally experience within ourselves a cause of our bodily motion. It is called

soul In many religious and philosophical traditions, there is a belief that a soul is "the immaterial aspect or essence of a human being". Etymology The Modern English noun '':wikt:soul, soul'' is derived from Old English ''sāwol, sāwel''. The ea ...

, mind, or spirit. But, we do not experience a cause of motions inside of other bodies. The ultimate cause of the motion of all bodies is the mind of

God In monotheistic thought, God is usually viewed as the supreme being, creator, and principal object of faith. Swinburne, R.G. "God" in Honderich, Ted. (ed)''The Oxford Companion to Philosophy'', Oxford University Press, 1995. God is typically ...

. This is known through

metaphysics Metaphysics is the branch of philosophy that studies the fundamental nature of reality, the first principles of being, identity and change, space and time, causality, necessity, and possibility. It includes questions about the nature of conscio ...

and

theology Theology is the systematic study of the nature of the divine and, more broadly, of religious belief. It is taught as an academic discipline, typically in universities and seminaries. It occupies itself with the unique content of analyzing th ...

. Natural science is limited to

experiment An experiment is a procedure carried out to support or refute a hypothesis, or determine the efficacy or likelihood of something previously untried. Experiments provide insight into cause-and-effect by demonstrating what outcome occurs wh ...

s and

mechanics Mechanics (from Ancient Greek: μηχανική, ''mēkhanikḗ'', "of machines") is the area of mathematics and physics concerned with the relationships between force, matter, and motion among physical objects. Forces applied to objects ...

, but it assumes that God was the prime source of motion. The laws of motion, not the cause of motion, are established by natural science. Physicists explain and understand phenomena by showing how they agree with the laws of motion. Fictional, abstract, general terms such as force, action, and reaction are used in theories, formulas, and computations. These cannot be found in bodies.''Encyclopedia of Philosophy'', Vol. I, "George Berkeley", New York: Macmillan, 1972 Through our senses, we actually experience only the effects of moving or resting bodies. The natural scientist is concerned with experiments, laws of motion, mechanical principles, and rational deduction from those principles. The principle and cause of motion itself is a metaphysical, theological, and moral concern.

Nature of motion

Motion should not be considered as an abstraction, separated from

and

. It should not be analyzed into abstract ideas such as movement,

velocity Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity i ...

, and force. Mathematical considerations of spatial and temporal infinitesimals lead to

paradox A paradox is a logically self-contradictory statement or a statement that runs contrary to one's expectation. It is a statement that, despite apparently valid reasoning from true premises, leads to a seemingly self-contradictory or a logically u ...

es. Motion should not be equated with the cause of motion. To say that the quantity of motion is always conserved is to confuse motion itself with the force that causes motion. The force of the cause of motion is conserved. Motion is not an internal, living force in things. It is a lifeless, indifferent effect.

Motion in space

Absolute space contains no bodies. But, as such, it would not be observable. Nothing is denoted by the words "absolute space." Motion and space are

relative Relative may refer to: General use *Kinship and family, the principle binding the most basic social units society. If two people are connected by circumstances of birth, they are said to be ''relatives'' Philosophy *Relativism, the concept that ...

. They presuppose a relationship to some other body through which they are determined. For a wider view, it would be useful to consider motion relative to the

fixed star In astronomy, fixed stars ( la, stellae fixae) is a term to name the full set of glowing points, astronomical objects actually and mainly stars, that appear not to move relative to one another against the darkness of the night sky in the backg ...

s, which would be considered as being at rest, instead of to absolute space. Just as we cannot know absolute space, we cannot know whether the whole universe is at rest or is moving uniformly in a direction. To determine the true nature of motion, we must follow three rules: (1) distinguish mathematical hypotheses from the nature of things; (2) beware of abstractions; (3) consider motion as sensible or imaginable and be content with relative measures.

Communication of motion

Physical science is concerned only with mechanics. Therefore, it can be said that, in a collision, action and reaction are always opposite and equal. Such actions and forces, though, are only mathematical hypotheses. We only really know that the striking body loses motion and the struck body gains motion. We do not know if the motion is communicated from one body to another or if the motion is destroyed in the striker and is created in the struck. In the true nature of things, all bodies are passive. The truly active cause of motion is metaphysical and not the concern of physical science.

References

External links

The Works of George Berkeley
in English on Project Gutenberg, incl. ''De Motu'' {{authoritycontrol 1721 works Scientific essays Works by George Berkeley