The Russian Orthodox idea of a kind of Saint who is a Fool for Christ, or for God, is a clue to a very important spiritual path.
The Fool is one who is not concerned with his status, his prestige, the opinions of normal, secular, sensible people - he is unworldly; the Fool for God is a type of fool - one who combines this deep indifference to worldly estimation with a simple and solid devotion to God.
A fool could be himself, or her-self, very simple or extremely intelligent; indeed the concept of a highly intelligent fool is one of particular importance and particularly neglected.
But the fool is not gullible - at least not in the usual sense - because gullibility is mostly about using greed and conceit to lead people against their own interests - to their too-late regret. This is hard to achieve with a fool, since his lack of pride makes him intrinsically unpredictable; and the fool is prone to accept what seem like bad outcomes as actually being good.
At a lower level, there are those who are a fool for their vocation - for science, or literature perhaps. This usually comes across in their attitude to criticism, and to being called a fool (which of course they will be); especially when they are disdained by their professions.
The fool for science, or poetry, will take unjust criticism from socially-dominant inferiors without resentment - with a shrug, with unspoken pity; will simply move onto other and more compelling subjects - recognising there is no defence against the accusation of being a fool.
One either is a fool - in which case there is no need for defence; or one is not a fool - and this is shown by the resentment and self-justifying against those who make the accusation.
You see - to be a fool really is a good thing - especially in the modern secular world; to be called a fool is a deep compliment - but only the fool knows it!
If a real fool was to decline the title, it would only be through modesty; with a blush and a hanging of the head - never with anger or vehemence.
Of course, people may pretend to be a fool, in order to manipulate others or get out of trouble (like the Good Soldier Sjvek) - or to claim a higher spirituality like some fake gurus of the 1960s counter-culture (who accepted the general appellation of fool; while raking in sexual benefits, ego-tripping on their inter-personal dominance, secretly sniggering at the gullibility of others).
But the real fool is innocent. Sometimes he may be protected by his innocence, and sometimes it may get him into trouble - but so long as he remains a fool he will remain innocent.
It is, however, a very sad thing to see someone who is born with the gift of foolishness squandering it in an unconvincing attempt to make other people 'take him seriously'.
Many of the greatest bores and the most aggressively egotistical people are those who are defying their destiny as fools.
The real fool, who is secure in his own foolishness, is a great gift to the world - and this includes the intellectual fool.
The unworldliness of a fool is itself a witness to higher things - to feel, to act, to be 'not of this world' is itself evidence of another world.
Note - The illustration is from the Rider-Waite deck of Tarot cards; which constitutes a remarkable, unique and inspired set of illustrations with inexplicable wisdom, mystery and depth.