He closes his discussion of the attributes by intimating that he has more to say on this topic, but had better be content with what has been said so far, for a more thorough discussion of these matters in a book might do harm to those who do not understand and interpret the author's words incorrectly. This reminds us of Maimonides's adjuration of the reader to keep what he finds in the "Guide of the Perplexed" to himself and not to spread it abroad. Philosophy clearly was a delicate subject and not meant for intellectual babes, whose intellectual digestion might be seriously disturbed.[239] We have now concluded our theory of God and his attributes; and in doing so we made use of principles of physics, such as matter and form, potentiality and actuality, motion and infinity. The next step is to prove the existence and nature of intermediate spiritual beings between God and the corporeal objects of the superlunar and sublunar worlds, called angels in the Bible, and secondary causes by the philosophers. For this purpose we shall have to apply the principles we have proved concerning the soul and the motions of the heavenly bodies. We have proved above that the human soul is at first in the child intelligent potentially and then becomes intelligent actually. This requires an agent, in whom the end to which the potential is proceeding is always actual. As the rational soul is neither body nor a corporeal power, this actual agent cannot be either of these, hence it is neither a sphere nor the soul of a sphere, but it must be a simple substance called _Active Intellect_. The prophets call it "Holy Spirit" ("Ruah Ha-Kodesh"). We thus have a proof of the existence of at least one such simple intellectual substance, or angel, the relation of which to the human soul is as that of light to vision. Without light vision is potential, light makes it actual. So the active intellect makes the potential soul actual and gives it first the axioms, which are universally certain, and hence could not have originated by induction from experience.