Having accepted the reality of physical object the Jainas naturally accepted the possibility of real motion.
Motion has always been an unintelligible perplexity to the Idealist. Both in the East and the West. Idealistic thinkers have fought shy of this by taking refuge in the conception of maya or appearance. It is in the western system of thought that the conception figures prominent. Zeno trying to defend the unchangeable adamantine Absolute of Parminides introduced four invincible arguments against the reality of motion. These arguments were accepted as invincible for several centuries. They figure in some form or other in Kantian antinomies and Hegelian dialectic. Even Bradley draws upon Zeno's wisdom in his attempt to condemn the realities of concrete world to the limbo of appearances. As Mr.B. Russel points out the arguments are no more irrefutable in the light of modern mathematics. Hence Realism need not approach the problem with any misgivings. Reality of motion has thus obtained a standing ground in the field of modern philosophy.
What is more important than this is the part played by this concept in Science. For Science, the world of reality is a system of energies. This dynamic conception of science has given a new dignity to the concept of motion. In spite of the unwarranted caution exhibited by Physicists like E.Mach and Karl Pearson, modern physics has once again emphasised the importance and the reality of motion in understanding the mystery of Nature. Always looked upon with suspicion by idealistic metaphysics, the doctrine of Reality of motion has been welcomed by Realistic and scientific systems of thought.
But in order to accept the reality of motion of Physical objects the reality of space must be postulated. Thus motion in Jaina doctrine is intimately associated with space and two other Categories with peculiar nomenclature, of dharma and adharma. We shall examine the Jaina account of these three Categories.
Reality of space is also a crucial doctrine to determine whether metaphysics is idealistic or realistic. Curiously the non-Jaina Indian systems of thought do not pay any prominent attention to the problem of space. In fact the more influential Indian system of Philosophy, the Vedata uses the term akasa indifferently to denote space and ether. It is the latter meaning that is more prominent. It is to the credit of the ancient Jaina thinkers that they tool a bold attempt to attack the problem and that with great success. This fact is perhaps due to their special interest in mathematics. An adequate solution of the problem of space and time is intimately connected with mathematical philosophy. It is modern mathematics that has successfully reclaimed once again space and time from the destructive dialectic of the idealistic metaphysics. Space is indispensable to science and realistic metaphysics. The wonders of modern science are all associated with the reality of space and what is contained therein. Hence to "the Indian Realism" space cannot but be real. Akasa is infinite extension. It accommodates all other real existences. On account of this accommodating function it has a portion which is filled with the other real objects. This portion is called lokakasa the world space because it is co-extensive with the world or Loka. Beyond that there is the infinite empty space which is suddha ananta akasa.
The interesting fact about this conception of space is the doctrine that space also is constituted by simple elements known as akasanu or spacial point. This akasanu is to space what pudgala-paramanu is to matter. And each akasanu is related to each pudgalanu. To borrow a convenient modern expression the class of space points and the class of material points are "similar having one to one relation".