This unity is God, the universal substance, - the one and only principle, or causa immanens, - that which is in things and yet is distinct from them as the universal is distinct from the particular.
We must have a causa essendi.
Europe had sinned in the face of God; otherwise Jerusalem would never have fallen; and the idea of a spiritual reform from within, as the necessary corollary and accompaniment of the expedition of Christianity without, breathes in some of the papal letters, just as, during the conciliar movement, the causa reformationis was blended with the causa unionis.
The germ of this dealing with a major causa may be found in the practice of the Arian emperors in the 4th century.
It is not enough to have for middle term a causa cognoscendi merely.
On the eve of that council he published at Naples his Causa El onorii Papae, which aimed at demonstrating the moral and historical impossibility of papal infallibility.
His great work is a treatise against the Pelagians, entitled De causa Dei contra Pelagium et de virtute causarum, edited by Sir Henry Savile (London, 1618).
He also wrote: Della Causa delle Febbri maligni (Pisa, 1658); De Renum usu Judicium (Strassburg, 1664); Euclides Restitutus (Pisa, 1658); Apollonii Pergaei Conicorum libri v., vi.
Thus God, the causa sui, manifests himself in an infinite multiplicity of particular modes.
According to Lotze, the connexion required by reciprocity requires also that the whole of every reciprocal action should take place within one substance; the immaterial elements act on one another merely, as the modifications of that substance interacting within itself; and that one substance is God, who thus becomes not merely the primary but the sole cause, in scholastic language a causa immanens, or agent of acts remaining within the agent's being.