"the beloved ought to accept the non-lover when he might have the
lover, because the one is sane, and the other mad. It might be so if
madness were simply an evil; but there is also a madness which is a
divine gift, and the source of the chiefest blessings granted to men.
For prophecy is a madness, and the prophetess at Delphi and the
priestesses at Dodona when out of their senses have conferred great
benefits on Hellas, both in public and private life, but when in their
senses few or none. And I might also tell you how the Sibyl and other
inspired persons have given to many an one many an intimation of the
future which has saved them from falling. But it would be tedious to
speak of what everyone knows. There will be more reason in appealing
to the ancient inventors of names, who would never have connected
prophecy which foretells the future and is the noblest of arts, with
madness, or called them both by the same name, if they had deemed
madness to be a disgrace or dishonour; —they must have thought that
there was an inspired madness which was a noble thing; for the two
words are really the same, and the distinguishing letter τ is only a
modern and tasteless insertion. And this is confirmed by the name
which was given by them to the rational investigation of futurity,
whether made by the help of birds or of other signs —this, for as much
as it is an art which supplies from the reasoning faculty mind the
prophetic frenzy of the Oracle of Delphi and the priestesses of Dodona
(the gift of Apollo) mystical revelations and initiations, which
provide "a way of release for those in need" (the gift of Dionysus [ie mysticism])
poetic inspiration (the gift of the Muses) the madness of lovers (the
gift of Aphrodite and Eros)."
-Socrates in Plato's Phaedrus
“Madness, provided it comes as the gift of heaven, is the channel by
which we receive the greatest blessings. The men of old who gave
things their names saw no disgrace or reproach in madness; otherwise
they would not have connected it with it the name of the noblest of
arts, the art of discerning the future, and called it the manic art.
So, according to the evidence provided by our ancestors, madness
is a nobler thing than sober sense - madness comes from God,
whereas sober sense is merely human.”
―Plato, Phaedrus
"those are called fortunate who although irrational succeed in
whatever they start on. And it does not pay them to deliberate, for
they have within them a principle of a kind that is better than mind
and deliberation (whereas the others have reason but have not this):
they have inspiration, but they cannot deliberate. For although
irrational they attain even what belongs to the prudent and
wise—swiftness of divination: only the divination that is based on
reason we must not specify, but some of them attain it by experience
and others by practice in the use of observation; and these men use
the divine. For this quality discerns aright the future as well as
the present, and these are the men whose reason is disengaged. This
is why the melancholic even have dreams that are true; for it seems
that when the reason is disengaged principle has more strength— "
-Aristotle, On Sense and the Sensible
"There is always some madness in love. But there is also always some
reason in madness."
-Nietzsche, Thus Spake Zarathustra, pt1 ch7
"Much madness is divinest sense
To a discerning eye;
Much sense the
starkest madness.
’Tis the majority
In this, as all, prevails.
Assent, and you are sane;
Demur, —you’re straightway dangerous,
And handled with a chain."
-Emily Dickenson
Mystics, divines, lovers, and poets, don't declare that they have a divine madness. That would be an act of self-consciousness that would undermine the declaration. They instead are possessed, by something transcendental, transpersonal, which by puppetting them reveals the parochial and humdrum nature of our ordinary sanities.
In love, it is our genes, or biological concerns that are an absolute prerequisite for where we find ourselfs arrived, which we experience in the rapture of love as a supervenient intrusion that overawes mumbling ordinary logic (see Is the tyrannicide perpetrated by William Tell morally legitimate?). Mysticism and prophecy are out of style, but I suggest they are about relating to things that will outlast our own lives (see What are some philosophical works that explore constructing meaning in life from an agnostic or atheist view?). And a poet grasps what Alan Watts describes, "The meaning and purpose of dancing is the dance" (see If everything ends one day why don't we end it today?).
There are things which precede rationality, and we can see here that we call them kinds of madness. But like Emily Dickinson says, echoing Foucault in 'Madness and Civilisation', we call certain expressions of madness that construct a world the majority accept, sane or real, and choose to ignore that there are other ways to engage. Hume says we cannot get an Ought from an Is, yet we don't wish to be reminded too often that there are alternatives to what our local community has settled on as how we ought to behave; and we call those who demur too much or too often, mad.
But without those expressing, in Socrates' sense a 'divine madness', we could not relate to the transcendental, the transpersonal. Diogenes, holding a lamp up in the sunshine to try to see an honest man, or Nietzsche's Zarathustra holding his lamp in the marketplace and asking "How could we drink up the sea? Who gave us the sponge to wipe away the entire horizon? What were we doing when we unchained this earth from its sun?"
The 'madness' of poetry allows the arrival at things more true than ordinary thinking; and gestures at the arrival at new logics from pre-logic. See Trying to Understand Quote by Nietzsche, and Surfaces and Essences: Analogy as the Fuel and Fire of Thinking.
Isn't 'sanity', only that part of madness we refuse to question? Like a mystic or prophet, we know intuitive certainties, but unlike them we feel ours secured by agreement with a majority.
Look at Jung's synchronicity for how we can agree on events, but disagree on how to group them, and what they point to. See modern mystic Rupert Sheldrake, who questions Is The Sun Conscious, and uses that to point at how if we don't dare to ask 'mad' questions we might remain incapable of making sense of 70% of the universe (Dark Matter as accounted for by volitional movements of stars). Godel Incompleteness points to how a reframing is always possible from outside the system, that can make a larger sense out of what was previously undecidable, in a new logic.
We should retain a respect for divine madness, out of a humble recognition of the limits to what we call sane, or real, that history will show were neither.