For the moment let us define the NATURE OF THE GOOD as far as the immediate purpose demands.
The Good is that on which all else depends, towards which all Existences aspire as to their source and their need, while Itself is without need, sufficient to Itself, aspiring to no other, the measure and Term of all, giving out from itself the Intellectual-Principle and Existence and Soul and Life and all Intellective-Act.
All until The Good is reached is beautiful; The Good is beyond-beautiful, beyond the Highest, holding kingly state in the Intellectual-Kosmos, that sphere constituted by a Principle wholly unlike what is known as Intelligence in us. Our intelligence is nourished on the propositions of logic, is skilled in following discussions, works by reasonings, examines links of demonstration, and comes to know the world of Being also by the steps of logical process, having no prior grasp of Reality but remaining empty, all Intelligence though it be, until it has put itself to school. Enneads I,8,2
For, once more, the NATURE OF THE GOOD is not such as to make it all things or a thing among all: that would range it under the same classification with them all and it would differ, thus, only by its individual quality, some specialty, some addition. At once it becomes not a unity but a duality; there is one common element not good and another element that is good; but a combination so made up of good and not good cannot be the purely good, the primarily good; the primarily good must be that principle in which the better element has more effectively participated and so attained its goodness. Any good thing has become so by communion; but that in which it has communion is not a thing among the things of the all; therefore the Good is not a thing of the All. Enneads V,5,13