In discussions about
space and time, the name relationalism (or relationism) refers to
Leibniz's relationist notion of space and time as against
Newton's
substantivalist views. According to
Newton’s substantivalism, space and time are entities in their own right, existing independently of things. Leibniz's relationism, on the other hand, describes
space and time as systems of relations that exist between objects. More generally, in physics and philosophy, a
relational theory is a framework to understand
reality or a
physical system in such a way that the positions and other properties of objects are only meaningful relative to other objects. In a relational
spacetime theory, space does not exist unless there are objects in it; nor does time exist without events. The relational view proposes that space is contained in objects and that an object represents within itself relationships to other objects. Space can be defined through the relations among the objects that it contains considering their variations through time. This is an alternative to an
absolute theory, in which the space exists independently of any objects that can be immersed in it. The relational point of view was advocated in physics by
Gottfried Wilhelm Leibniz and
Ernst Mach (in his
Mach's principle). It was rejected by
Isaac Newton in his successful description of
classical physics. Although
Albert Einstein was impressed by Mach's principle, he did not fully incorporate it into his
general theory of relativity. Several attempts have been made to formulate a full Machian theory, but most physicists think that none have so far succeeded. For example, see
Brans–Dicke theory.
Relational quantum mechanics and a relational approach to quantum physics have been independently developed, in analogy with Einstein's
special relativity of space and time. Relationist physicists such as
John Baez and
Carlo Rovelli have criticised the leading
unified theory of
gravity and
quantum mechanics,
string theory, for retaining absolute space. Some prefer a developing theory of gravity,
loop quantum gravity, for its 'backgroundlessness'. ==Relationalism (colour theory) ==