Descartes died when Newton was eight years old, but his philosophies were becoming immensely fashionable as Newton entered university and extended his reading beyond the curriculum. Because it contained material referring to his disputed theories of divine function in a mechanical universe, Descartes's most famous book, Discourse on the Method (published in 1637), was unpopular with the ecclesiastical authorities, but his theories were discussed openly in the more liberal universities of Europe and began to spread.
As Descartes's theories of dualism became known, three other philosophers were helping to create the intellectual scene to which Newton would add his own unique ideas.  So, by the middle of the seventeenth century, as Newton was preparing to enter the academic world, natural philosophy was in a state of flux. The old notions of Aristotle still provided the traditional backbone of university study in the areas of logic, astronomy and natural philosophy, but this was primarily because of an old school of influential academics. Gradually, radical ideas from the Continent were eroding the Greek philosopher's supreme position. According to one historian of science, 'From being a realm of substances in qualitative and teleological relations, the world of nature had definitely become a realm of bodies moving mechanically in space and time.'
It was within this climate of change that Newton entered university in 1661 and took the first steps towards finding his own path through the shifting philosophies of the time and establishing his own views.  His religious beliefs were immersed in Arianism.  This was the doctine of Arius which was pronounced heretical at the Council of Nicea.  Arius asserted that Christ was not of one substance, but a creature raised by God to the dignity of Son of God.
By the early years of the eighteenth century Newton began to formulate a link between aspects of Arianism and the means by which gravity operates. During the early 1700s he had begun a fragmentary passage in which he explored the nature of Christ's body and form before and after his earthly incarnation.
He had after his resurrection such a body as he had before his incarnation. And therefore as his [natural] mortal body by the resurrection became an immortal body, so his immortal body by the incarnation became a mortal one. And it is easy to believe the one as the other.
According to Arian doctrine, Christ stood somewhere between God and man in the universal hierarchy. Jesus was immortal and 'the first created', but theological notions were hazy when it came to Christ's form. Was he a spiritual being who could take on the mantle of physical existence, or was he material? As Newton entered the final years of his life, he began to accept the idea that Christ possessed a 'spiritual body'. Writing sometime during the late 1710s to early 1720s, he declared:
And he who by his resurrection has changed his mortal flesh into immortal spiritual body might by his incarnation change his immortal spiritual body into a body of flesh. For whereas the Father is the invisible God whom no eye hath seen nor can see and therefore is totally incorporeal, the Son before his incarnation and the Holy Spirit have appeared in visible shapes upon several occasions and therefore have spiritual bodies.
Elsewhere he stated repeatedly that 'God does nothing by himself which he can do by another.' So, he had concluded, God does not himself control directly the gravitational forces that keep the planets in motion, nor does he provide directly the medium via which universal gravitation operates. Instead, the incorporeal ether which facilitates the phenomenon of gravitation (and perhaps other forces) is actually the body or spiritual form of Jesus Christ.
Of course Newton had no means of proving this hypothesis - it was principally a faith- based concept: a notion derived from his Arian convictions - but it described neatly the way in which God could preside over his creation without dirtying his hands by direct contact with the physical world. Christ was a mediator for all action in the universe, the intermediary via which the system of the universe was maintained, God's 'commander- in-chief', his viceroy.
To clarify his thoughts on the subject, sometime around 1720 Newton wrote what he perceived as a personal credo, a form of amalgamation of science and religion - a guide, perhaps, for future explorers. This included a clear picture of the role he saw for Christ in the universal scheme of things - not least the function of the spiritual body of Jesus as the medium by which celestial mechanics was maintained. 'Jesus was beloved of God before the foundation of the world,' he wrote, 'and had glory with the father before the world began and was the principle of the creation . . . the agent by whom God created all things in this world.''
To summarise, the spiritual body of Jesus, the first created, was the facilitator for the creation of the physical universe, provided the means via which the cosmos continued to function mechanically, and acted as a medium via which forces acted at a distance without any visible, tangible, measurable mechanism.
This was a concept that Newton refined and distilled during his final years. Although no means of proof could be elucidated, and even he had doubts at times about the details of this system, it was the fullest explanation of gravitation he could arrive at. If it did nothing else, it acted as a prop - it was a comforting model that could be neither proved or disproved but could serve to fill one of  the gaps in a model of the universe that had been so successful in every practical and empirical sense.