Evidence indicates a date early in the 360’s for both ep. 9 and Contra Eunomium, the Trinitarian works of Basil of Caesarea.
It is commonly acknowledged that Basil of Caesarea’s thought about the Trinity changed at some point in the 360s. Naturally, the chronological ordering of Basil’s early theological works will reveal the nature of the change in his thought and account for the subsequent evaluation of it. Basil’s ep. 9 and Contra Eunomium are especially important here because they preserve a great deal of what Basil has to say about the Trinity. But according to the way in which most date these works, the change in his thought is not a gradual progression culminating in Nicene orthodoxy but Basil’s purposeful misrepresentation of his own position so as to hide his true thoughts in the interest of imperial and ecclesiastical politics.