Foolishness is the unawareness or lack of social norms which causes offence, annoyance, trouble and/or injury. The things such as impulsivity and/or influences may affect a person's ability to make otherwise reasonable decisions. In this sense, it differs from stupidity, which is the lack of intelligence. An act of foolishness is called folly.
Andreas Maercker in 1995 defined foolishness as rigid, dogmatic, and inflexible thinking which makes feelings of bitterness and probable annoyance. It is considered the foundation of illusions of grandiosity like omniscience, omnipotence and inviolability.
The Book of Proverbs characterizes traits of foolishness. Foolishness and wisdom are contrasted in Paul's letter to the Corinthians. He condemns intellectual arrogance and advocates a humble attitude instead of foolishness, in which it is then possible to learn.
Plato transvalued reason over foolishness, to him integrity of acceptance of a state itself was the beginning of wisdom, he said "He is the wisest man who knows himself to be ill-equipped for the study of wisdom".
All this invites a question. Even if Paracelsus's foolishness, like Erasmus's and Brant's, were metaphorical, surely metaphor only works by its relationship to some positive referent, i.e. a small, pre-existing, pathological group? At the opposite end of the foolishness spectrum from the universal, Paracelsus does indeed identify a limited group which is, if not pathological, then odd. But it does not match the intellectual disability model. In Erasmian fashion it has several guises, and can be traced back to earlier sources. Since metaphor was not just a literary device but could also be explanatory, the narrative slips from universal foolishness to this more specific state and back without any sense that somewhere reality ends and metaphor begins.
those born foolish and insipientes [unwise], who show signs of foolishness immediately as infants by a habit of mimicry exceeding that of other infants and are not submissive or amenable, so that often they do not learn to speak, much less to take on functions requiring industriousness. This evil is frequent in particular regions, as written about in Egypt and in the village of Bremis in the Valais as I myself have seen, and in the Pinzgau valley in Carinthia; many in addition to their foolishness tend to have a poorly shaped head and a goitre, are dumb with a huge swollen tongue and present a deformed sight sitting in the streets gazing at the sun, putting sticks in the spaces between their fingers, writhing about with mouths wide open, moving passers-by to laughter and amazement.44
The heaviest concentration of the Hebrew words referring to foolishness is in the Wisdom literature, where the fool is constantly contrasted with the wise. The fool is not so much stupid (except when the context demands such a meaning) as immoral and pernicious. The fool's problem is not so much intellectual as practical and spiritual. In fact, the terms "wise" and "fool" are used by the sages to designate respectively the faithful and the sinners. This characterization is well depicted in the competition between Wisdom and Folly for the attention and loyalty of the young man. Folly is a seductress who seeks to allure the young man away from the wife of his youth ( Prov 5:18 ). She personifies more than stupidity. She is immorality and adultery ( Prov 6:23-35 ; 7:6-27 ; 9:13-18 ). The fool is the naive person who succumbs to her amorous overtures.
Paul makes frequent ironic reference to foolishness, particularly in 1 and 2 Corinthians. He deprecates the wisdom of the world, which characterizes God's action in Jesus as nonsensical and scandalous. Human understanding erroneously takes God's wisdom to be foolishness and God's strength to be weakness since God's actions do not fit human reason or expectation. Indeed, from a worldly perspective God uses the foolish thing and calls the foolish person ( 1 Cor 1:27-28 ).
This negative attitude toward foolishness is understandable when its practices are observed. Among these practices are: relying on earthly wealth ( Luke 12:20 ); failing to recognize that the ministry of Jesus is God's visitation to claim his own bride ( Matt 25:1-13 ); turning away from the gospel of grace to legalism ( Gal 3:1-3 ); worshiping the creature rather than the Creator ( Rom 1:18-23 ); and abrogating the demands of God with meaningless distinctions ( Matt 23:16-22 ). Perhaps even more significant than the above characteristics is a failure to act on the words of Jesus by building a house without an adequate foundation ( Matt 7:26-27 ), and a failure to believe the good news of Jesus' resurrection ( Luke 24:25 here the foolish are described as "slow of heart" the Old Testament expression is "without heart, " without understanding, as in Prov 9:16 ). The believer is not to be foolish, but to "understand what the Lord's will is" ( Eph 5:17 ).
And he said, What comes out of a person is what defiles him. For from within, out of the heart of man, come evil thoughts, sexual immorality, theft, murder, adultery, coveting, wickedness, deceit, sensuality, envy, slander, pride, foolishness.