Studies some doctrinal similarities between aspects of the philosophical theology of the Latin athor Marius Victorinus (c. 290-c.364CE) and the Arabic works of the great Islamic philosopher, theologian and physician Avicenne (Ibn Sīnā, 980-1037 CE). It is suggested that Avicenna encountered materials in the Neoplatonica Arabica, some of which may derive from Porphyry, which contained some form of the distinction between essence and existence. These materials served as the starting point for Avicenna's development of his own complex and highly influential doctrine of the distinction beteen essence and existence