Withdraw into yourself and look. And of you do not find yourself beautiful yet, act as does the creator of a statue that is to be made beautiful: he cuts away here, smooths there, he makes this line lighter, this other purer, until a lovely face has grown upon his work. So do you also: cut away all that is excessive, straighten all that is crooked, bring light to all that is overcast, labour to make all one glow of beauty and never cease chiselling your statue, until there shall shine out on you from it the godlike splendour of virtue, until you shall see the perfect goodness surely established in the stainless shrine.
When you know that you have become this perfect work, when you are self-gathered in the purity of your being nothing now remaining that can shatter that inner unity, nothing from without clinging to the authentic man, when you find yourself wholly true to your essential nature, wholly that only veritable Light which is not measured by space, not narrowed to any circumscribed form nor again diffused as a thing void of term, but ever unmeasurable as something greater than all measure and more than all quantity—when you perceive that you have grown to this, you are now become very vision: now call up all your confidence, strike forward yet a step—you need a guide no longer—strain, and see.
This is the only eye that sees the mighty Beauty. If the eye that adventures the vision be dimmed by vice, impure, or weak, and unable in its cowardly blenching to see the uttermost brightness, then it sees nothing even though another point to what lies plain to sight before it. To any vision must be brough an eye adapted to what is to be seen, and having some likeness to it. Never did eye see the sun unless it had first become sun-like, and never can the Soul have vision of the First Beauty unless itself be beautiful.
Plotinus, Enneads, I.6.9 (translated by Stephen MacKenna)