Early Aristotelian universes were finite in extent, formed by concentric spheres that ended at the sphere of fixed stars. In contrast, the Stoic universe was a finite universe with an exterior void that was infinite.
Simultaneously, ideas concerning God and the universe became increasingly grand and inflated. Medieval theology developed far-reaching concepts concerning the nature of God that subsequently were transferred to the nature of the universe. Theological ideas of God as unconfined, infinite and simultaneously everywhere were translated into scientific ideas of the universe as unconfined, infinite, and having its center everywhere ~ Edward Harrison, Cosmology: The Science of the Universe
God is an infinite sphere whose centre is everywhere and circumference nowhere ~ Empedocles
The fabric of the world has its centre everywhere and its circumference nowhere ~ Nicholas of Cusa, On Learned Ignorance
Rene Descartes refused to use the word ‘infinite’ to describe the universe, as, according to him, only God could be infinite. In the Cartesian universe, space can only exist where there is matter, so physical space as well matter both extended indefinitely. Isaac Newton responded to Descartes by saying that ‘where there is no matter, spirit endows space with extension‘. Newton argued that to say space cannot exist without matter was to deny the presence of God in the universe. Isaac Newton therefore originally believed in a Stoic universe in which God created a material system of finite extent, with an infinite void in which the Spirit of God inhabited. However, he changed his mind after exchanging correspondences with a certain Richard Bentley. This Richard Bentley was a clergyman who used the Newtonian system in his lectures as proof of the existence of the divine. He consulted Isaac Newton on some technical points, and wondered about the effects of gravity in a finite distribution of stars. This stunned Isaac Newton into rethinking his position, as a finite system of stars would eventually collapse into a single mass due to the pull of gravity. The universe, therefore, had to have an infinite system of stars, so that the effects of gravity would be cancelled out.
During the the Victorian era in the 19th century, there occured a reversal in opinions. The development of better telescopes and more observational studies of the heavens led to the discovery of fuzzy clouds in space called nebulae. Immanuel Kant, a German philosopher and scientist, had proposed a hierarchical universe in which a group of stars formed a larger system, which combined with other systems to form even larger systems – in what was referred to as the ‘many island universe’. This view was shared by Thomas Wright. The question was whether these fuzzy nebulae were galaxies with their own collection of stars similar to our own Galaxy in a many island universe, or if these nebulae were clouds of gas within our own Milky Way Galaxy (as proposed by Pierre Simon de Laplace) in a Stoic-like universe (also known as the ‘one island universe’). Further observations by astronomers such as William Huggins seemed to reveal that these nebulae were excited gas rather than stars – sounding the death knell of the Wright-Kantian universe of many islands. They had found the answer, or so they thought.
Agnes Clerke, a leading historian of astronomy in the 19th century, wrote in her book The System of the Stars: No competent thinker, with the whole of the available evidence before him, can now, it is safe to say, maintain any single nebula to be a star system of coordinate rank with the Milky Way. A practical certainty has been attained that the entire contents, stellar and nebular, of the sphere belong to one mighty aggregation, and stand in ordered mutual relations within the limits of one all-embracing scheme – all-embracing that is to say, so far as our capacities of knowledge extend. With the infinite possibilities beyond, science has no concern.
Of course, we now know that the idea of a one-island universe is wrong. With further advancements in optical technology, astronomers have discovered that some of the fuzzy clouds were indeed systems of stars and gas much like our own Milky Way. This is another reminder that we should never be too confident with regards to some of our current cosmological theories. At the dawn of the 21st century, the question of whether we live in a finite or infinite Universe remains unanswered.
Nicholas of Cusa in the fifteenth century distinguished between unlearned and learned ignorance. In unlearned ignorance, the less we know, the more confident we are in the truth of our knowledge. In learned ignorance, the more we know, the less confident we are in the truth of our knowledge. ~ Edward Harrison, Cosmology: The Science of the Universe