The Book of Proverbs gives advice on the best way to achieve a contented life and a high standard of personal morality. Those who can achieve this are called ‘the wise’ who are righteous, but those who cannot are ‘the fools’ who are wicked. Psychiatric interest lies in the description of the latter. Unfortunately, the single word ‘fool’ in the St James's version (as well as in all later editions) was used as the English translation for eight separate Hebrew words, each of which described a quite distinct character. In this way the elaborate ancient Hebrew character typology was effectively lost in translation.

The main types of Hebrew fool were: kesil (literally, stupid and over-confident), an unintelligent person frequently involved in quarrels; ewil, a morally blind individual, but more intelligent than kesil; pethi, a simpleton, perhaps with intellectual disability, who cannot plan for the future; the hasar-leb (literally, empty-hearted), also of poor intelligence, who neglects himself and his property. Other characters are also occasionally mentioned: ba-ar, a crude individual; nabal, a brutal and depraved man (the word nabal also means wine skin suggesting a link with alcoholism); holel, an irrational madman; les, also translated as a scoffer, was a contemptuous narcissistic individual while belial (a scoundrel) was an aggressive psychopath who shows most of the features of DSM–IV antisocial personality disorder. Finally, a female character essa zarah, the strange woman or loose woman, a loud, rebellious person, constantly on the go, has numerous affairs and shows both borderline and histrionic features.

A much more detailed description and analysis of each of these character types, some of whom resemble DSM–IV personality disorder types, is given by Fox (Proverbs 1–9. The Anchor Bible, vol. 18A; Doubleday, 2000), who wrote that the fools of the Book of Proverbs were ‘aberrant individuals, just stupid folk who [caused] harm above all to themselves and whose punishment [was] inevitable’. This definition will seem familiar to most psychiatrists who work with people with personality disorders. It is also not too far from Schneider's original definition (in his 1923 title Die Psychopathischen Personlichkeiten) of an individual with a personality disorder as ‘a person who suffers or makes others suffer because of his abnormal personality’. The Book of Proverbs and its character typology was written more than 2500 years ago.