Ante-Nicene Fathers, Vol VIII:
Pseudo-Clementine Literature.: Chapter LXVI

Chapter LXVI.—Existence and Conception.

To this Simon replied: 669   “O thou who hast woven a web of many frivolities, listen now.  It is impossible that anything which comes into a man’s thoughts should not also subsist in truth and reality.  For things that do not subsist, have no appearances; 670 but things that have no appearances, cannot present themselves to our thoughts.”  Then said Peter:  “If everything that can come into our thoughts has a subsistence, then, with respect to that place of immensity which you say is outside the world, if one thinks in his heart that it is light, and another that it is darkness, how can one and the same place be both light and darkness, according to their different thoughts concerning it?”  Then said Simon:  “Let pass for the present what I have said; and tell us what you suppose to be above the heavens.”

Footnotes

[The remaining chapters of this book hare no exact parallel in the Homilies.—R.]

That is, have no visible or sensible species, according to the Platonic theory of perception.