In the seventeenth century, theÂ philosophy of space and timeÂ came as a central issue inÂ epist andÂ metaphysics. At its heart,Â Gottfried Leibniz, the German philosopher-mathematician, andÂ Isaac Newton, the English physicist-mathematician, set out two opposing theories of what space is. Rather than being an entity that independently exists over and above other matter, Leibniz held that space is no more than the collection of spatial relations between objects in the world: “space is that which results from places taken together”.
Space could be thought of in a similar way to the relations between family members. Although people in the family are related to one another, the relations do not exist independently of the people.Â Leibniz argued that space could not exist independently of objects in the world because that implies a difference between two universes exactly alike except for the location of the material world in each universe. But since there would be no observational way of telling these universes apart then, according to theÂ identity of indiscernibles, there would be no real difference between them. According to theÂ principle of sufficient reason, any theory of space that implied that there could be these two possible universes, must therefore be wrong.