 In his philosophical writings, More elaborated a philosophy of spirit which explained all the phenomena of mind and of the physical world as the activity of spiritual substance controlling inert matter. More conceived of both spirit and body as spatially extended, but defined spiritual substance as the obverse of material extension: where body is inert and solid, but divisible; spirit is active and penetrable, but indivisible. It was in his correspondence with Descartes that he first expounded his view that all substance, whether material or immaterial, is extended. He went on to argue space is infinite, anticipating that other native of Grantham, Isaac Newton, and that God who is an infinite spirit is an extended being (res extensa). In Enchiridion metaphysicum, he argues that the properties of space are analogous to the attributes of God (infinity, immateriality, immobility etc.).